1955 Buick Dynaflow Specifications

1955 Buick Dynaflow Specifications


The 1954 Twin Turbine Dynaflow transmission has been redesigned, the major feature being the incorporation of a stator with variable pitch blades. The new stator gives the equivalent of a passing gear with no gear change; and is accomplished by changing the angle (pitch) of the stator blades.

The stator blades function in either of two positions; low angle for low stall R.P.M., or high angle for high stall R.P.M.

In low angle position, engine speed will be reduced for a given car speed throughout the conversion range. In the high angle position, performance is increased for two reasons: first, the converter torque multiplication ratio is increased to 2.5 to 1. Second, the transmission allows the engine to “rev-up” to the speed where it develops maximum torque, thus utilizing the engine in its most favorable condition for performance.

Stall speeds and torque ratios of the Dynaflow transmission for the past few years, incorporating different converters, are given in the following table:

1955 Buick Dynaflow Torque

1955 Buick Dynaflow Torque

The new variable pitch Dynaflow torque converter automatically provides the proper ratio of torque multiplication to meet the varying demands imposed by starting and driving under all ordinary conditions of load and grade, in addition to added performance for acceleration and passing when needed. The transition to performance range is fluid smooth since it is accomplished without the use of selective gears.


  1. Converter Pump and Cover

The converter pump has been modified to include thirty bosses cast around the circumference of the pump flange, fifteen for pump cover bolts and fifteen for balance weight rivets, and the flange thickness provides increased pump strength. Each balance weight is now attached with one rivet and two pump cover bolts.

The converter pump cover has been redesigned to include an enclosed hub and baffles spot welded to the inside of the cover. The baffles on the inside of the cover tend to equalize thrust forces of the transmission while the enclosed hub will reduce the possibility of oil leaks. See figure 5-l.

1955 Buick Dynaflow Converter Pump and Cover

1955 Buick Dynaflow Converter Pump and Cover

  1. Twin Turbine Assembly

The Twin Turbine assembly is basically the same as 1954 except that the sun gear of the planetary unit is no longer coupled to the stator.

The new sun gear is supported on the reaction shaft by a bronze bushing and a sprag type of free wheeling clutch. The clutch assembly is housed inside the sun gear and retained in place by the rear thrust washer. The clutch holds the sun gear stationary to give gear reduction from the first to second turbine, then when both turbines reach the same speed, the sun gear free wheels so that it will not interfere with Twin Turbine operation.

  1. Variable Pitch Stator

Twenty stator blades, mounted on individual crankpins, are supported in the assembly by a carrier ring at the outer ends and the carrier assembly at the inner (or crank) ends. The carrier assembly consists of two matched pieces, a front carrier and rear carrier, which are held together by five screws. The inner mating surfaces of the carrier contain matched grooves which serve as bearing surfaces to support the stator crankpins.

The front carrier forms a hub to support the assembly on the reaction shaft and contains ports through which oil flows to the front of the stator piston. The rear carrier and free wheel cam form a housing for the stator piston, to which the inner ends of the crankpins are attached by a snap ring, so that movement of the piston in either direction rotates the stator blades. The free wheel cam closes the rear end of the carrier assembly and utilizes free wheel rollers and springs. The cam is retained in position by a snap ring and three driving keys identical to the keys used in the clutch assembly.

1955 Buick Dynaflow Converter Planetary Gears and Stator

1955 Buick Dynaflow Converter Planetary Gears and Stator

The function of the stator, when stationary, is to change the direction of oil flow from the turbine to the proper angle for smooth entrance into the converter pump, so that all energy remaining in the oil may be utilized to increase pump output, and to provide converter “cruise” or “performance” range, depending on stator blade angle.

  1. Operation of the Variable Pitch Converter

Operation of the variable pitch converter is the same in low and reverse, however in direct drive the converter is designed to provide the equivalent of a passing gear without gear change. This is accomplished by changing the angle of the stator blades to either a “low angle” (cruise) or “high angle” (performance) position. Under cruising conditions in drive range the stator blades will be in “low angle” or nearly parallel to the axis of the assembly. This provides the largest opening between the blades for freedom of oil movement through the stator and minimum amount of redirecting the converter oil flow. See figure 5-3.

1955 Buick Variable Pitch Stator

1955 Buick Variable Pitch Stator

Under performance conditions in drive range, the stator blades will be in “high angle” or like a venetian blind partially closed, figure 5-3. This provides the greatest redirecting of converter oil flow and the resultant higher converter torque multiplication.

The converter transmits torque to the direct drive clutch and planetary gears through the transmission input shaft. Direct Drive, Low and Reverse range of the transmission is determined by control of the clutch and gears. The converter ranges of “cruise” (low angle) and “performance” (high angle) is determined by the angle of the stator blades and is controlled through linkage incorporated in the throttle control mechanism.

Description of the torque converter operation will begin with car stationary, transmission in direct drive, stator blades in “low angle” (due to throttle position) and the engine running at idling speeds. At this point the converter pump is slowly turning with the engine, and the turbine members are stationary. The engine driven converter pump projects a rotating cylinder of oil into the first turbine, through which it flows into the second turbine. At idling speed the force of oil flow against the blades is not sufficient to move either turbine, therefore, the oil flows through the turbines into the stator without transmitting any appreciable amount of torque. See figure 5-4.

1955 Buick Dynaflow Torque Converter

1955 Buick Dynaflow Torque Converter

As the oil emerges from the second turbine near its center, the backward curvature of the exit ends of the blades causes the oil to spin backward with reference to pump rotation as it flows into the stator. Pressure of oil against the forward face of the stator blades causes the free wheeling clutch to lock and hold the stator stationary. The stator blades then change the direction of flow so that the oil enters the pump rotating in the same direction as the pump is turning.

While the engine is running at idling speeds the oil continues to flow from the pump, through the turbine and stator and back into the pump in the circuit just described. A gentle circulation is created which does not transmit appreciable torque, although a light movement or creep of car may sometimes be produced.

When the throttle is opened, the engine speeds up and rapidly approaches its torque peak. With increased speed, the converter pump now projects a large volume of oil into the turbines at high rotary speed. The rotating cylindrical mass of oil may be compared to a spinning flywheel rim. A spinning flywheel has stored up energy (turning force) which may be transmitted to any mechanism which opposes its rotation. Since the vanes of both turbines oppose rotation of the spinning flywheel of oil projected from the pump, the stored up energy in the oil exerts a powerful impulsion force against the vanes tending to rotate the turbines in the same direction as the pump.

At this stage the impulsion force of the oil against the vanes is not sufficient to move either turbine. The oil flows through the turbine channels and is discharged into the stator, which re­ directs it into the pump entrance.

At this point the stator blades may be in either “low angle” or “high angle” position, depending upon the position of the accelerator pedal linkage. However, the principles of converter operation are the same.

As oil emerges from the second turbine into the stator, spinning at high speed in a reversed direction, it exerts a powerful reaction force against the turbine vanes, tending to rotate the turbine in the same direction as the pump.

(A reaction force

[rearward] is always exerted by a fluid which is moving in any direction under pressure. It is reaction force which tends to kick back the nozzle of a fire hose when a stream of water emerges under pressure. Reaction force causes the recoil of a fired gun, the flight of a rocket, and the flight of a plane equipped with a jet engine.)

Engine torque applied to the converter pump generates a given amount of energy in the oil projected from the pump against the turbine vanes. When the turbines are stationary, the oil passes through both turbines and the stator and returns to the pump with almost as much energy as when projected. The amount of energy in the oil thereafter projected from the pump becomes the sum of the energy in returning oil plus the energy resulting from engine torque application, or almost double the amount of energy that could be generated by engine torque alone. The greatly increased energy in the spinning flywheel of oil then projected into the turbines produces a corresponding increase in the impulsion and reaction forces upon the turbine vanes.

The described build-up of forces produces a turning force or torque upon the turbines which is much greater than the torque produced by the engine; therefore, torque multiplication is accomplished. It would seem that torque multiplication would increase indefinitely as the cycle repeats itself, but mechanical factors limit the increase in torque multiplication beyond a definite ratio in any given torque converter design.

The build-up of forces against the turbine vanes causes the first turbine to rotate in the same direction as the converter pump. The first turbine absorbs part of the energy transmitted by the oil stream and converts this energy into torque, which is imparted to the ring gear in its hub. The ring gear rotates the planet pinions, in the opposite direction and this turning force is transmitted to the converter sun gear. Forces, tending to rotate the sun gear opposite to pump rotation, cause the sun gear free wheeling clutch to lock and hold it stationary, then the planet pinions “walk” around the sun gear so that turning force is applied to the turbine carrier in which the pinions are mounted. The second turbine absorbs energy from the oil stream after it leaves the first turbine and converts this energy into torque which is also imparted to the turbine carrier, on which this turbine is mounted. The turbine carrier transmits the torque of both turbines to the input shaft to which it is splined.

The turbine planetary gear set gives a ratio of 1.6 to 1 when the sun gear is stationary and this reduction gearing increases the torque transmitted through the first turbine. The overall operation of the Variable Pitch Torque Converter provides a maximum torque multiplication of approximately 2.10 to 1 at low stall R.P.M. (car stationary and engine accelerated under load) when the stator vanes are in the “low angle” or cruise position. When the stator vanes are in the “high angle” or performance position, the maximum torque multiplication available through the converter is 2.50 to 1 at high stall R.P.M.

Usually the car may be started with appreciably less than the maximum torque multiplication that is available through the converter. For unusually severe conditions, Low range may be used to provide an overall maximum torque multiplication of approximately 4.55 to 1 stall.

As the car gains speed and momentum, the demand for torque decreases so that the applied torque causes turbine speed to rapidly approach pump speed. As this occurs it is essential for torque multiplication to taper off so that car speed can be maintained at a lower, more economical engine speed. Tapering off occurs automatically because centrifugal force generated in the rapidly rotating mass of oil in the turbines creates an outward counter force which opposes the flow of oil from the pump. Reduction of oil flow and pump output energy effects a decrease in the impulsion and reaction forces upon the turbine so multiplication of engine output torque tapers off as turbine speed increases.

Reduction in speed differential between turbines reduces the torque reaction on the sun gear until this reaction is entirely eliminated. This action reverses the force, holding the sun gear stationary and it begins to free wheel in the same direction as the ring gear and turbine carrier.

As speed of the second turbine increases, the direction of oil flow into the stator correspondingly changes toward the rear faces of the stator vanes, thus gradually eliminating the force holding the stator stationary.

Pressure against the forward face of the stator vanes and torque reaction against the sun gear, ceases at approximately the same speed, after which the stator and gear free wheels. When the sun gear is released by the free wheeling clutch, the first turbine ceases to be effective and the speed of the second turbine has increased until both turbines are rotating together at nearly the same speed as the pump. During this same period the speed of the free wheeling stator increases and approaches turbine speed so that it presents little or no interference with the flow of oil between the second turbine and the pump.

At this point the torque converter functions as an efficient fluid coupling, transmitting torque at a 1 to 1 ratio. Sufficient speed differential remains between pump and turbines to enable transfer of oil from pump to turbines where the oil gives up energy and returns to the pump for recirculation.

The various stages of stator and pump operation described do no£ occur at set speeds but are dependent on torque requirements imposed by car operating conditions, or driver manipulation of the stator blade angle by means of throttle control mechanism.

With light load and steady driving, torque multiplication may cease at very low car speeds, but with continued acceleration some degree of torque multiplication may be present throughout the major portion of the car speed range. When the torque converter is operating as a fluid coupling and car operating conditions change so that in­ creased torque is demanded, the converter can automatically adjust itself to meet the demand without any manipulation of controls by the driver; however, if the driver desires additional performance for passing, he may change the pitch of the stator blades through manual control.

When the drive through the torque converter is reversed on deceleration or when descending grades, the converter functions as a fluid coupling to permit effective engine braking. It also functions as a fluid coupling when the car is pushed in Low range to crank the engine.


  1. Reaction Shaft Flange Assembly

The reaction shaft flange has been redesigned to accommodate installation of the new variable pitch stator, free wheeling sun gear assembly and the new needle bearing in the direct drive clutch.

The reaction shaft is larger in diameter and extends through the flange to provide an inner race for the needle bearing which supports the direct drive clutch. See figure 5-5.

1955 Buick Clutch Needle Bearing and Reaction Shaft

1955 Buick Clutch Needle Bearing and Reaction Shaft

The shaft provides a bearing surface for the stator and sun gear. A babbitt bearing, retained inside the shaft by two snap rings, supports the front of the input shaft.

Oil passages in the reaction flange have been relocated to utilize direct drive clutch oil pressure, from the high accumulator, to control the angle (pitch) of the new variable pitch stator.

  1. High Accumulator

The high accumulator has been redesigned and now includes a stator control valve, which is contained in a separate cylinder of the high accumulator body. The cylindrical stator valve has two lands which control passage of oil through ports in the accumulator body. A coil spring bears against the bottom of the valve, the upward travel of which is limited by a threaded stop in the top of the casting. The valve is operated by a crank, the inner end of which contacts the upper edge of the valve while the outer end is connected to external linkage by a crank operating lever.

The operating crank is retained in position by a threaded bearing which contacts two tangs on the shaft of the crank. A rubber seal, around the operating crank at the bearing, and a copper gasket at the threaded plug prevents escape of oil. See figure 5-6.

1955 Buick Dynaflow High Accumulator Parts

1955 Buick Dynaflow High Accumulator Parts

  1. Direct Drive Clutch and Planetary Gear Set

The direct drive clutch is supported on a needle bearing instead of the bronze bushing previously used. (See figure 5-5.) The low range reaction gear has been recessed and the reverse sun gear has been reduced in thickness to accommodate a thicker thrust washer between these parts, as shown in figure 5-7.

1955 Buick Recessed Reaction Gear and New Thrust Washer

1955 Buick Recessed Reaction Gear and New Thrust Washer

The new thrust washer is selective to provide control of end play of the units within the transmission case, the adjustment of which is described under the heading, “Adjustment of Output Shaft End Play”, covered later.

If an older type reaction gear requires replacement, and new recessed gear is used, the reverse sun gear and thicker thrust washer must also be used.

  1. Rear Bearing Retainer

The transmission control detents have been relocated from Transmission Control Lever Housing to the Rear Bearing Retainer in the trans­ mission. This provides a better control of the Transmission Shift Control Valve and more positive range position, having a smooth, solid feeling when shifting. Locating the detents in the trans­ mission prevents slight movement of the shift control valve as the engine moves on its rubber mounts.

A detent plate, added to the valve operating cross shaft engages a spring loaded roller and support assembly to provide positive engagement. See figure 5-8.

1955 Buick Rear Bearing Retainer

1955 Buick Rear Bearing Retainer


Operation of hydraulic controls remains the same as 1954 in low and reverse, however when the transmission is in direct drive range, additional controls are necessary to change the angle (pitch) of the stator blades.

  1. Stator Hydraulic Control.

A stator control valve in the high accumulator body is actuated by linkage incorporated in the throttle control mechanism. The linkage is constructed so that the stator valve remains in the upward position until the carburetor throttle valves have reached a predetermined opening, at which time the linkage moves the stator valve down to shift the stator blades to the “high angle” position.

When the shift control valve is in direct drive position, oil under pressure (approx. 90 PSI) is routed through the high accumulator to the direct drive clutch. Some of this oil, under pressure, is directed through a restricted passage in the reaction flange into the upper stator port valve in the high accumulator body.

With the stator control valve up, the top and center ports in the accumulator are open while the lower ports are closed. This directs oil between the valve lands into the reaction flange, through passages to the reaction shaft. Oil then flows through ports to the front side of the stator piston. See figures 5-9 and 5-10.

1955 Buick Stator Hydraulic Control Circuit-Low Angle

1955 Buick Stator Hydraulic Control Circuit-Low Angle

1955 Buick Oil Flow to and from Accumulator-Low Angle

1955 Buick Oil Flow to and from Accumulator-Low Angle

High clutch oil pressure, on the front side of the stator piston, is greater than converter charging pressure (against the rear side of the piston) so the piston moves back in the stator carrier, rotating and holding the stator blades in the “low angle” (open) position. The variable pitch stator will remain in this position, in drive range, as long as throttle control mechanism does not operate to change the position of the stator control valve.

If throttle linkage is operated beyond a predetermined setting, stator control linkage is actuated to force the stator valve down against spring tension. This closes the upper ports in the accumulator body, cutting off oil pressure to the front side of the stator piston, and opens the lower port and stator apply line for discharge to the sump.

With no pressure on the front of the stator piston, converter charging pressure moves the piston forward to rotate the stator blades approximately 75 degrees to the “high angle” (closed) position. See figures 5-11 and 5-12.

1955 Buick Oil Flow to and from Accumulator-High Angle

1955 Buick Oil Flow to and from Accumulator-High Angle

1955 Buick Stator Hydraulic Control Circuit-High Angle

1955 Buick Stator Hydraulic Control Circuit-High Angle

In low and reverse ranges, the stator blades remain in the “high angle” position as there is no high accumulator pressure to the stator assembly, regardless of throttle position. In direct drive range, the stator blades can be in either the “low” or “high angle” positions depending on throttle position. In low and reverse range, the linkage has no effect on vane position because there is no pressure at the high accumulator and the vanes are always in the “high angle” position.

For information regarding linkage operation and adjustment, see Throttle And Stator Control Link­ age-Group 3.

  1. Converter Feed, Oil Cooler and Lubrication Systems

When either oil pump is running, oil flows in limited volume through the converter, oil cooler, and lubrication system.

Oil flows from the pressure regulator valve through a channel containing a restricted metering orifice to limit the volume, and enters the converter around the outside of the reaction shaft and between the stator and converter pump. All parts in the torque converter are lubricated by the oil which completely fills the converter.

As oil leaves the converter it enters the input shaft just forward of the reaction shaft, flows through input shaft to an exit port, between two oil rings, in the input shaft. From this point, passages in the reaction shaft and flange direct the oil to an external oil cooler which maintains oil temperature at a satisfactory level.

Oil is piped from the cooler to a passage in the rear bearing retainer which connects with the lubrication system and is regulated to approximately 15 Lbs. PSI by a lubrication pressure regulator valve.

Lubricating oil, for the direct drive clutch and planetary gear set, enters the output shaft just forward of the rear pump, flows through both shafts and into each unit. The passage in the center of the output shaft also extends back to lubricate the rear bearing retainer bushing and universal joint.


The Dynaflow test and inspection, Par. 5-9, 1954 Shop Manual remains the same except for addition of testing the stator pressure.

  1. Checking Stator Pressure

Before making the pressure test, oil level must be correct and the transmission must be thoroughly warmed up to operating temperature. Place rear end of car solidly on car stands or use a free wheel type hoist so that plugged ports can be reached and transmission can be operated with rear wheels free to turn.

Front pump and high accumulator pressures should be checked before testing the stator pres­ sure because oil pressure for stator operation is taken from the clutch apply line at the high accumulator.

If, when checking high accumulator pressure, it is noticeably low, the cause may be in either the accumulator or the stator circuits. To determine which is at fault, disconnect the stator operating rod at the high accumulator. Make certain the stator valve operating lever is properly positioned and tight on the stator valve operating crank, then raise the lever against the stop pin, while noting the gauge reading.

If gauge reading remains the same, the trouble is in the high accumulator and may be caused by external or internal leakage past accumulator body gas et. A rise in accumulator pressure, with the lever against the stop pin, indicates a leak in the stator control circuit. To check stator pressure, remove pipe plug from the reaction flange adjacent to the high accumulator and connect gauge J-2575. Operate engine with transmission in drive range at 500 RPM, 1000 RPM, and 1800 RPM; the pressures on the following table should be obtained:

1955 Buick Dynaflow Pump Readings

1955 Buick Dynaflow Pump Readings


  1. Control Mechanism In Steering Column

Dynaflow transmission controls are completely new for 1955. In order to streamline the steering column, the directional signal switch has been redesigned, the shift control is completely new, and the shift detent assembly has been moved from the steering column to the rear bearing retainer. The shift indicator has been relocated farther down the mast jacket just in front of the instrument panel.

The control lever is entirely new in operation. The pivot point of the shift lever is between the handle and control lever shaft, so when the handle is pulled back toward the driver, the shaft moves down to release it from the stops. The stop plate is welded to the mast jacket, no angular adjustment being required. Travel required to engage and disengage the stops is adjusted by means of a threaded pin on the trans­ mission control shaft lever.

  1. Dynaflow External Linkage Adjustment

NOTE: Because Stator Control Mechanism and Throttle Control Mechanism are dependent upon each other for proper operation, Stator Control Linkage Adjustment must begin at the carburetor; therefore this adjustment is described in paragraph 3-3 “Throttle and Stator Control Linkage Adjustment”.

  1. Adjustment of Shift Control Mechanism at Lower Lever and Stop Plate.
  • With transmission in “D” (drive) position, .010″ to .020″ clearance must exist between stop pin and the large opening in the stop plate. See Figure 5-13.
    1955 Buick Lower Lever and Stop Plate Adjustment

    1955 Buick Lower Lever and Stop Plate Adjustment

  • If specified clearance does not exist, adjust the shift rod clevis pin to obtain proper clearance.




  1. Removal of Transmission

Removal procedures remain the same as out­ lined in the 1954 Shop Manual except for disconnecting the external linkage to the Stator Control Valve at the High Accumulator.

  1. Installation of Transmission

Installation procedures remain basically the same as 1954 except for adjustments. The following adjustments should be made on the transmission as indicated below:

  1. Shift detent mechanism adjustment is made prior to installation of transmission as described during assembly in Par. 5-10, Sub Par. I and k.
  2. Stator Control Mechanism adjustment is described in Par. 3-3.
  3. External Linkage adjustments are described in Par. 5-7.


  1. Removal of Converter and Bell Housing

NOTE: This operation is not required for removal of valve and servo body, universal joint, or rear bearing retainer.

  1. Remove both drain plugs from converter pump cover to drain any oil remaining in converter.
  1. Remove all nuts, plain washer, and bolts attaching cover to converter pump. A punch inserted through bell housing hand hole into a drive bolt hole will hold pump from turning.
  2. Remove cover from pump. Check cover seal for damage or evidence of oil leak before removing it from cover.
  3. Remove reverse band adjustment cover and shift transmission into “Parking”. Pry up on reverse band operating lever with screw driver to lock input shaft, then remove bolt, lock washer, retaining washer, and thrust washer from hub of turbine and input shaft.
  4. Remove Twin Turbine assembly. A screw driver inserted into a hole in the first turbine disk will aid in removal.
  5. Before removing sun gear, check to see if sun gear free wheels when rotated clockwise (facing converter) and locks on shaft when attempt is made to rotate it counterclockwise, then slide sun gear forward off the shaft. See figure 5-14.
    1955 Buick Stator and Sun Gear

    1955 Buick Stator and Sun Gear

  6. Pull stator slowly forward on reaction shaft. Then with stator installing tool J-5806 in position as shown in figure 5-15, reach behind stator and hold thrust washer, spacer, rollers, and springs in position while sliding stator forward off the reaction shaft and on special tool.
    1955 Buick Removal of Stator Assembly

    1955 Buick Removal of Stator Assembly

  7. Pull the converter pump forward from the reaction shaft and immediately check for evidence of oil leakage. Radial streaks of fresh oil on back of pump and fresh oil streaks on face of front oil pump body indicate leakage past the oil pump seal.
  8. Before removing the bell housing check to see whether all attaching bolts are tight. Loose bolts may be the cause of oil leakage at this point.
  9. Place bell housing over edge of bench and remove it. Examine the rubber oil seal located around the front oil pump to see whether it has been uniformly compressed by the bell housing; if not, check for any obstacle that may be around the oil pump or opening in bell housing that would prevent uniform compression of the seal.

NOTE: The front oil pump can only be removed after the reaction shaft flange has been removed.

  1. Disassembly of Torque Converter Units

NOTE: Disassembly of the torque converter units is essentially the same as 1954 except for the new sun gear and variable pitch stator.

(Disassembly of Sun Gear)-See figure 5-16.

1955 Buick Converter Sun Gear Parts

1955 Buick Converter Sun Gear Parts

  1. Remove thrust washer (with tangs) from face of gear.
  2. Using a suitable tool, carefully pry flanged thrust washer from gear.
  3. Remove free wheeling clutch (sprag) from inside of sun gear. (Disassembly of Variable Pitch Stator.)
  1. With stator placed on bench, remove steel thrust washer and selective spacers, then remove special tool J-5806, free wheel rollers and springs, using care to prevent loss of parts.
  2. Pry cam retaining snap ring from groove in stator carrier, then remove free wheel cam with three driving keys. Figure 5-17.
    1955 Buick Removing Stator Free Wheel Cam

    1955 Buick Removing Stator Free Wheel Cam

  3. Turn stator over and remove five special screws and lock washers (figure 5-18), using special screw driver J-5826, then lift front stator carrier from assembly.
    1955 Buick Removing Stator Carrier Screws

    1955 Buick Removing Stator Carrier Screws

    CAUTION: Do not use blade of any type to pry apart front and rear carriers.

  4. Remove snap ring and thrust washer which retain stator crankpins in contact with stator piston, then lift stator blade carrier ring and stator blades from rear carrier assembly. See figure 5-19.
    1955 Buick Removing Stator Carrier Front

    1955 Buick Removing Stator Carrier Front

  5. Remove stator piston from rear carrier assembly, c. Inspection of Torque Converter Parts

NOTE: In addition to the inspection procedures outlined in the 1954 Shop Manual, Par. 5-15 (Sub. Par. b ) observe the following:

  1. Condition of stator blade assemblies for distortion, excessive wear, cracks, or other damage.
  2. Condition of free wheel cam and rollers. Remove any nicks or burrs with an Arkansas Stone and polish with crocus cloth.
  3. Check free wheel roller springs for loss of tension. Weak springs should be replaced.
  4. Condition of piston oil seal ring and bore for excessive wear or scoring.
  1. Assembly of Torque Converter Units

(Assembly of Sun Gear )

  1. Install free wheel clutch (sprag) in bore of sun gear with shoulder on clutch toward the outside. See figure 5-20.
    1955 Buick Converter Sun Gear Ports

    1955 Buick Converter Sun Gear Ports

  2. Position flanged thrust washer over clutch and gear, then carefully press washer squarely in place. (Use new washer if necessary.)

CAUTION: If a plastic hammer is used to tap washer in place, use care to prevent damage to thrust washer.

  1. Install front thrust washer with tangs entered in holes of gear.

(Assembly of Variable Pitch Stator )

  1. Be certain oil sealing ring is in place on stator piston, then carefully install piston in carrier so that protruding end of piston, when seated, extends through the grooved end.

NOTE: Slightly tilting the piston, as it is installed, will assist in assembly.

  1. With the protruding end of piston and grooved side of carrier up, place assembly on a suitable block so that the piston is held firmly seated. (Compressor ring of clutch spring compressor J-2590 provides a suitable support.)
  2. Place stator blade carrier ring on bench with perforated edge in ring up, then insert the stator blades in the carrier ring with the cranks toward the center and the dished side up. When assembled, the blades should be in the nearly closed position as shown in figure 5-21.
    1955 Buick Stator Blade Installation

    1955 Buick Stator Blade Installation

  3. Carefully lift the stator blade carrier ring with stator blades, lower it over the carrier and piston so that stator blade crankpins are aligned with carrier grooves, using care to prevent blades from dropping out of ring. See figure 5-22.
    1955 Buick Installing Stator Carrier Ring and Blades

    1955 Buick Installing Stator Carrier Ring and Blades

  4. If necessary shift carrier ring slightly to position stator blade crankpins in carrier grooves.
  5. Install stator blade crank thrust washer and snap ring in groove in stator piston.
  6. Be certain that no burrs or foreign material exist on mating surfaces, then position front half of carrier over rear half so that dowels and screw holes are lined up. Install star lock washers and screws, using screw driver J-5826.
  7. Check stator blades for smooth operation. Blades should reach both low and high angle position without binding or locking. If stator blades do not rotate freely within the full range of travel, it is probably due to misalignment of crankpins in the stator grooves.
  8. Turn assembly over and install the stator free wheel cam, three driving keys and snap ring.
  9. Check and, if necessary, alter free wheel springs to obtain uniform height, then install free wheel rollers and spring. (Position rollers at rounded end of cams.)
  10. Place Installer J-5806 in hub of stator so that flat end is flush with rollers, to prevent rollers dropping out. Slight rotation of tool will assist in installation.
  11. Be certain spacers, thrust washer, and cam surface is free of grease and dirt, then align holes in spacer with tangs on washer and install them with tangs entering the stator cam holes.
  1. Installation of Bell Housing and Converter Units.
  1. Install front oil pump seal ring around pump body against pump cover.
  2. Install bell housing, using lock washers on bolts and stud. Sparingly coat threads of lower right side bolt with Permatex No. 3 because the bolt hole opens into transmission case. Tighten bolts and stud nut evenly to 35-40 ft. lbs. torque.
  3. Place converter pump on a suitable support with open end up. Carefully place stator in proper position, with original spacers and thrust washer between stator and pump. (Grease should not be used to hold thrust washer and spacers in place as this will affect the clearance check described below.)
  4. Place sun gear in position with tanged thrust washer up, then carefully lower Twin Turbine assembly in place, being certain the planet pinions mesh properly with the sun gear.
  5. Place converter clearance gauge J-5899 on converter pump as shown in figure 5-23.
    1955 Buick Checking Converter Clearance-on Pump

    1955 Buick Checking Converter Clearance-on Pump

    Loosen wing nut and firmly press plunger down against first turbine hub, then tighten wing nut.

  6. Support the converter pump cover on bench with inside surface up and bronze thrust washer in place. Then remove converter clearance gauge from converter pump, invert it, and center it on the cover as shown in figure 5-24.
    1955 Buick Checking Converter Clearance-on Cover

    1955 Buick Checking Converter Clearance-on Cover

  7. Attach dial indicator KMO-30-B to sleeve KMO-30-K then mount indicator on the gauge post so that indicator button is contacting the upper rim of the gauge plunger. (See figure 5-24.) Set dial to zero.
  8. Loosen plunger wing nut and firmly press plunger down against thrust washer, noting the gauge reading.
  9. The dial should read between .017″ and .030″ counterclockwise from zero, because the distance measured is existing clearance between the converter units and the pump cover.
  10. If the indicator does not read within specified limits, change the spacer thickness between the stator and converter pump to obtain proper clearance.

Increasing spacer thickness will decrease clearance and decreasing spacer thickness will increase clearance. Spacers are available under Group 4-117 as follows:

Part No. – Thickness
1167710 – 010″-.013″
1167711 – 020″-.023″
1167712 – 030″ -.033″

  1. Install converter pump on reaction shaft, turning it until lugs on pump hub enter the slots in front oil pump driving gear.
  2. Be certain all rollers and springs are in stator assembly and tangs of thrust washer are properly positioned through the spacer holes and into stator; then with stator installer J-5806 in hub of stator, (see figure 5-15) position assembly so that stator will slide off tool and on reaction shaft. Be certain thrust washer and spacers remain in position until stator is seated against converter pump. Petroleum jelly between spacers will assist in retaining them in position during installation.
  3. Install converter sun gear with tanged thrust washer toward the front. If (sprag) clutch assembly is properly installed, the sun gear may be rotated in a clockwise (facing converter ) direction only.

NOTE: Before proceeding, be certain snap ring is on input shaft.

  1. Install Twin Turbine assembly on input shaft, turning it as required to mesh the planet pinions with the sun gear.
  2. Place second turbine retaining washer on input shaft bolt, then screw bolt into input shaft with selective thrust washer between retaining washer and first turbine hub. Tighten bolt to 30-35 ft. lbs. torque.
  3. Using a feeler gauge, check clearance between selective thrust washer and first turbine hub. Clearance should be between .002″ and .009″. See figure 5-25.
    1955 Buick Checking Turbine Clearance

    1955 Buick Checking Turbine Clearance

If specified clearance does not exist, select washer of proper thickness. The following thrust washers are available:

Part No. – Thickness – Marked
1166112 – .060″-.063″ – 6
1166113 – .067″-.070″ – 7

  1. Looking at front face of converter pump cover, select the three bolt holes (X) that are aligned with the center of the hub and one of the counterbored recesses adjacent to hub. Mark these holes for later installation of the flywheel-to-pump driving bolts. See figure 5-26.
    1955 Buick Location of Driving Boll Holes

    1955 Buick Location of Driving Boll Holes

  2. Install a new O-ring seal on pump cover, making sure that surfaces are clean and that seal has even tension all around and is not twisted.
  3. Grease the bronze washer so it will adhere and place it in recess in cover, then install cover on pump so that the three marked driving bolt holes are not aligned with any hole in pump rim at which a balance weight is located.
  4. Install bolts with plain washers and special nuts in all but three driving bolt holes, insert the shank of a 11/32″ drill through one bolt hole to align all holes, then tighten bolts to approximately 5 ft. lbs. torque in numerical sequence shown in figure 5-27.
    1955 Buick Ball Tightening Sequence

    1955 Buick Ball Tightening Sequence

    Finally, tighten bolts in same sequence to 25-30 ft. lbs. torque.

When tightening bolts, insert a wide screw driver blade between flat side of bolt head and the pump to prevent a corner of bolt from digging into pump casting.


  1. Removal of Reaction Shaft Flange from Transmission Case

The removal procedures are unchanged except for the following item:

IMPORTANT: The first step in reaction shaft flange removal is the removal of the snap ring from the input shaft. See figure 5-28.

1955 Buick Removing Input Shaft Snap Ring

1955 Buick Removing Input Shaft Snap Ring

Following snap ring removal, proceed as outlined in the 1954 Shop Manual, Par. 5-14, Sub. Par. E.

The front oil pump retaining bolts enter the pump from the clutch side of the reaction flange, therefore the flange must be removed prior to removing the front oil pump.

  1. Removal and Installation of Input Shaft Bearing.
  2. Replacement of Clutch Needle Bearing
  1. Temporarily-mount front oil pump and cover on reaction flange to add support to flange while removing bearing.
  2. Remove outer retaining snap ring from front of bearing.
  3. Remove bearing, using remover J-5822 with handle and hammer of Tool J-1436, as shown in figure 5-29.
    1955 Buick Removing Input Shaft Bearing

    1955 Buick Removing Input Shaft Bearing

  4. If inner snap ring did not come out with remover, it may be left in place, however check to see if it is firmly seated in its groove. If loose, replace it.
  5. Place end of reaction shaft on block of wood, then using Input Shaft Bearing Installer J-5816 and light hammer, tap new bearing into position until shoulder of tool contacts reaction flange shaft. See figure 5-30.
    1955 Buick Installing Input Shaft Bearing

    1955 Buick Installing Input Shaft Bearing

  6. Install outer retaining snap ring.

Disassembly and assembly of direct drive clutch remains the same as 1954 except for removal and installation of clutch needle bearing which is a new part for 1955. The bearing may be removed and replaced as follows:

  1. With the clutch plates removed, place drum fiat on bench with open end down and drive bearing out through hub. (Power Steering Bearing Installer J-5191 will make a suitable remover and replacer.)
  2. With drum in same position and numbered side of bearing against Tool J-5191, drive bearing into place. The edge of the needle bearing race should be flush with beveled shoulder in clutch drum.
  1. Installation of Reaction Shaft Flange Assembly

The installation procedure of the reaction shaft flange assembly is unchanged except for the following adjustment, and the installation of the new input shaft snap ring which is the final assembly step.

  1. Adjustment for End Play of Output Shaft

An additional service adjustment is necessary on the 1955 Variable Pitch Dynaflow. This adjustment provides control of end play between the direct drive clutch, planetary gear set and trans­ mission case and tends to reduce the “clunk” when shifting from low to reverse and vice-versa.

A selective thrust washer has been installed between the reaction gear and the reverse sun gear. The reaction gear has been recessed and the reverse sun gear has been reduced in thickness to allow a thicker washer to be used. See figure 5-31.

1955 Buick Checking Output Shaft End Play

1955 Buick Checking Output Shaft End Play

  1. During assembly of transmission, just prior to installation of reaction flange, a thrust washer of proper thickness between the reaction gear on clutch assembly and reverse sun gear in planetary unit, must be selected.
  2. With clutch assembly in position and selective thrust washer with grooved side toward sun gear, temporarily install reaction flange, using gasket, and three or four bolts.
  3. Thread transmission end play gauge J-5804 into rear threads of output shaft, thread dial indicator extension rod J-5808 into threaded hole in rear bearing retainer flange, using a wrench to tighten rod, then attach “C” clamp, extension J-5339, sleeve KMO-30-K, and dial indicator KMO-30-B as shown in figure 5-31, making certain indicator extension bears against end of gauge.
  4. Push gauge J-5804 forward, as far as possible, set indicator at zero, then pull gauge toward indicator using sufficient force to remove end play from output shaft.
  5. The dial indicator should read between .020″ and .034″. If the reading is not within specified limits, remove reaction flange and clutch assembly and install a thrust washer of proper thickness.

Thrust washers are available in thicknesses as follows:

Part No. – Thickness
1168031 – 100″ to .103″
1168032 – 114″ to .117″
1168033 – 128″ to .131″
1168034 – 142″ to .145″

NOTE: If specified clearance cannot be obtained by using the selective thrust washers, recheck the other thrust washers and mating surfaces within the transmission case for dejects.

  1. When the proper thrust washer has been selected, reassemble the reaction flange to the case as outlined in the 1954 Shop Manual and install the input shaft snap ring.
  1. Disassembly and Assembly of High Accumulator
  1. Remove retaining pin and check ball from high accumulator body.
  2. Remove large pipe plug, cap, gasket spring and piston from body cylinder.
  3. Remove clamp bolt, crank operating lever, threaded bearing, seal gasket and operating crank from accumulator body.
  4. Remove piston stop plug, piston and spring. See figure 5-32.
    1955 Buick High Accumulator Parts

    1955 Buick High Accumulator Parts

  5. Wash parts in clean solvent, dry thoroughly, blow out all passages with air, examine all parts of accumulator for excessive wear, scoring or other damage.
  6. Remove any nicks or burrs from accumulator piston or stator control valve; however, do not round the sharp edges on piston and valve. If sharp edges are marred or rounded, foreign particles may wedge between the part and the body causing sticking.
  7. To reassemble, reverse the disassembly procedure, performing the following.
  • Lubricate the valve and piston before installation and do not tap or force parts into body.
  • Before tightening stator valve operating lever lock nut, be certain the crank is held against the piston, without depressing the spring, and the lever held against the stop as shown in figure 5-33.
    1955 Buick Stator Operating Lever Adjustment

    1955 Buick Stator Operating Lever Adjustment

  • Install new seals and gaskets where required.


  1. Disassembly of Rear Bearing Retainer
  2. Assembly of Rear Bearing Retainer
  3. Adjustment of Detent In Rear Bearing Retainer with Retainer Removed from Transmission Case
  1. Remove detent spring from inside of rear bearing retainer.
  2. Remove detent adjusting lever attaching nut, washer and lock bolt on outside of case, then remove lever.
  3. Using a plastic hammer, lightly tap the detent support shaft toward the inside of the case, then remove the detent roller lever support assembly. Discard the oil seal.
  4. Disconnect the parking lock operating rod from the cross shaft by unscrewing the rod end from the cross shaft lever. The rod end is provided with a lock washer.
  5. Disconnect the valve operating rod from the cross shaft, remove rod and retaining clip.
  6. Screw a 1/4″-20 bolt into the parking lock operating lever shaft and the lock pawl shaft and pull these parts from the bearing retainer, then remove the lock pawl and lever assembly.
  7. Remove cross shaft bearing and seal using a box wrench; (a socket which does not fully engage bearing or an end wrench will distort bearing.) Remove cross shaft.
  1. Install operating cross shaft assembly and cross shaft bearing, then install a new seal in the bearing with grooved side facing inward.
  2. Install parking lock pawl and lever assembly in rear bearing retainer, then install the lock pawl shaft and operating lever shaft with tapped end outward.
  3. Attach the operating rod to cross shaft and snap retainer in place, then connect the parking lock operating rod to cross shaft lever, using a lock washer on the threaded rod end.
  4. Install the detent lever and support assembly with new seal using care to prevent damage to oil seal.
  5. Install adjusting lever on support shaft on outside of case, then install lock washer and tighten nut on shaft. Install flat washer, lock washer and bolt at the slotted end of linkage adjusting lever. Do not tighten bolt at this time.
  1. Temporarily install shift lever on cross shaft, then shift the parking pawl into the park position as shown in figure 5-34.
    1955 Buick Shift Detent Adjustment

    1955 Buick Shift Detent Adjustment

  2. Raise or lower the adjusting lever at the slotted end until the pawl lock contacts the parking pawl, then tighten lock bolt on the adjusting lever, being certain contact is maintained. See figure 5-34.
  3. In this position the roller should be in the deepest portion of detent and the pawl lock should break contact at the same moment the detent roller begins to move toward neutral position.


  1. Installation of Rear Bearing Retainer

Installation of rear bearing retainer on the transmission case is made in the usual manner; however, the detent mechanism should be properly adjusted prior to installation.

Following installation of rear bearing retainer, the control valve linkage must be adjusted as outlined in Sub. Par. k below.

  1. Adjustment of Shift Detent Mechanism and Control Valve Linkage on Assembled Transmission

NOTE: If shift detent mechanism was adjusted prior to installation of rear bearing retainer on transmission, disregard Steps 1 through 3 and adjust control valve linkage beginning with Step 4. If transmission is installed in car, remove oil pan and disconnect rod from shift lever and proceed as follows:

  1. Use shift lever to operate shift linkage to make certain it works freely, then move lever toward front of transmission to engage parking lock pawl in ratchet wheel. Output shaft should be rotated to be certain parking pawl engages ratchet wheel.
  2. Shift the transmission to the neutral position, then with output shaft rotating, raise or lower detent adjusting lever as shown in figure 5-34 until the pawl begins to ratchet on the ratchet wheel, then move the adjusting lever in the opposite direction until ratcheting cannot be heard.
  3. Tighten lock bolt making certain that adjustment does not change. Recheck by rotating output shaft for sound of ratcheting.
  4. Move shift lever to the park position, making certain output shaft is locked, then push control valve (in valve body) away from stop pin (on servo body) just enough to remove play from linkage, then check clearance between stop pi n and end of valve, using a feeler gauge. Clearance should be .030″ to .040″.
  5. If clearance is not correct, loosen lock bolt on adjusting lever at valve lower operating lever and adjust to obtain proper clearance. See figure 5-35.
    1955 Buick Control Valve Linkage Adjustment

    1955 Buick Control Valve Linkage Adjustment

  6. Tighten lock bolt on adjusting lever, making certain clearance doesn’t change.
  7. Move shift lever to drive position, then note position of control valve. The end of the valve should be within 1/32″ (in either direction) from the edge of the hole in the body, with play removed from the valve. See figure 5-36.
    1955 Buick Position of Shift Control Valve-Drive Range

    1955 Buick Position of Shift Control Valve-Drive Range

  8. The valve body can be moved approximately 1/32″ in either direction by loosening the valve body bolts slightly and shifting the valve body on the servo body.


  1. Illustrations

To assist in parts identification, exploded illustrations of the entire 1955 Dynaflow transmission have been included in this group. Each part is identified by a list which accompanies the illustration. (Figures 5-37, 5-38, 5-39, and 5-40.)

1955 Buick Torque Converter-Exploded View

1955 Buick Torque Converter-Exploded View

1955 Buick Torque Converter-Exploded View Legend

1955 Buick Torque Converter-Exploded View Legend

1955 Buick Dynaflow Front Pump

1955 Buick Dynaflow Front Pump

1955 Buick Dynaflow Front Pump Legend

1955 Buick Dynaflow Front Pump Legend

1955 Buick Dynaflow Oil Cooler

1955 Buick Dynaflow Oil Cooler

1955 Buick Dynaflow Oil Cooler Legend

1955 Buick Dynaflow Oil Cooler Legend