1951 Buick Rear Axle Removal and Disassembly

1951 Buick Propeller Shaft Spline Oil Seal

On cars equipped with the 4.1 rear axle ratio it is not necessary to remove the rear axle assembly in order to remove the propeller shaft, since a puller is available for the pinion of this gear set.

Removal of 1951 Buick Rear Axle Assembly

1. Place car stands solidly under frame so that rear end of car is high enough to permit working underneath.
2. Disconnect parking brake cable at rear brake cable sheave and at bracket on front end of torque tube. Disconnect brake hose from pipe at frame X member and remove retainer. Plug hose and brake pipe openings to prevent entrance of dirt.
3. Disconnect torque tube from torque ball by removing bolts at flange.
4. Disconnect links from shock absorber arms and disconnect radius rod at right end.
5. Disconnect lower ends of rear springs. On Series 40 the attaching studs have right hand threads, but on Series 40-50-70, the attaching bolts have left hand threads.
6. Hoist rear end of car high enough to roll rear axle assembly out from under car.

Installation of 1951 Buick Rear Axle Assembly

1. Check universal joint torque ball for evidence of oil leakage and for wear of universal joint bushing. Note whether torque ball has end play or is excessively tight. Make any corrections indicated, following procedure given in paragraph 4-12.
2. Cement a new gasket in recess in front end of torque tube.
3. Roll 1951 Buick rear axle assembly under car, then rest car solidly on stands placed under frame, with rear end of car high enough to permit working underneath.
4. On Dynaflow Drive cars, place propeller shaft spline oil seal parts on front end of propeller shaft in the following order: spring retainer, spring, seal cap, oil seal. See figure 5-3. NOTE: Install these parts just before connecting torque tube to torque ball. Do not install part s before rolling axle assembly under car.
5. Connect torque tube to universal joint torque ball with bolts and lock washers.
6. Connect rear springs to rear axle assembly and connect links to shock absorber arms.
7. Connect brake hose to brake pipe at frame X member and lock in place with retainer. Connect parking brake cable to bracket on front end of torque tube and to brake cable sheave. Bleed rear wheel cylinders and adjust .parking brake as described in paragraphs 8-9 and 8-13.
8. Connect radius rod to 1951 Buick rear axle. NOTE: Normal weight of car must be on rear springs when tightening radius rod pin nuts so that rubber bushings in rod will be clamped in neutral position.

5-8 REPLACEMENT OF 1951 BUICK REAR AXLE STRUT ROD

The rear ends of strut rods are attached to axle housing by bolts. The front ends of strut rods are riveted to a bracket welded to the torque tube. Strut rods supplied for service replacement are not drilled for the attaching rivet; therefore the rivet hole must be drilled to coincide with hole in bracket after installation and alignment of strut rod. This cannot be done with 1951 Buick rear axle assembly under the car.

Replacement of Strut Rod – Series M-50-70

1. Remove rear axle assembly (par. 5-7).
2. Drill through the head of strut rod rivet with a 7/16″ drill; the rivet head has a centering depression for this operation. Drive out rivet with a punch. CAUTION: If rivet head is cut off without drilling, the hole in strut rod and bracket will be distorted.
3. Disconnect brake pipe and parking brake cable conduit from strut rod and disconnect strut rod from 1951 Buick rear axle.
4. Before installation of strut rod, scribe a line on bracket in line with the center of rivet hole. Using a pair of dividers set at 3 inches, locate a center-punch mark on the scribed line exactly 3 inches from center of rivet hole. See figure 5-4 view “A”.

1951 Buick Locating Rivet Hole in Strut Rod

Replacement of Strut Rod-Series 40

1. Remove 1951 Buick rear axle, drill out strut rod rivet and remove strut rod as described in subparagraph a, Steps 1, 2, 3 above.
2. Bolt rear end of new strut rod to axle housing, bringing nut up finger tight.
3. Hold front end of strut rod against bracket on torque tube so that rivet hole is centered on flat end of rod. Insert sharp scriber through hole in bracket to mark its location on strut rod.
4. Remove strut rod. Place center punch mark in exact center of scribed mark, then drill a 1/4″ hole, followed by a 1/2″ drill.
5. Reinstall strut rod, then run a 9/16″ drill through holes in strut rod and bracket.
6. Attach strut rod to bracket with bolt No. 1312923, 1/8″ lock washer and a thin nut. Tighten bolt at rear end of strut rod.

5-9 REPLACEMENT OF AXLE SHAFT, WHEEL BEARING, AND OIL SEALS

Removal of Axle Shaft

1. Place car stands solidly under 1951 Buick rear axle housing so that wheels are clear of floor, then remove rear wheel and brake drum.
2. Clean the rear end of chassis, bottom of body, axle housing, wheels and tires, and under rear fenders, removing as much dirt as possible.
3. Remove cover and drain rear axle housing.
4. Remove differential side pinion shaft lock screw, push pinion shaft from differential case, and remove spacer and pinions.
5. Push axle shaft inward and drive the horseshoe-shaped lock washer from grooved inner end of axle shaft, using Remover J 1515. See figure 5-5.

1951 Buick Removing Axle Shaft Lock Washer

Replacement of Wheel Bearing and Oil Seals

1. After removal of axle shaft, disconnect link from shock absorber arm.
2. Disconnect brake pipe from wheel cylinder and cover openings in pipe and cylinder with plugs or tape to exclude dirt.
3. Remove bolts holding brake backing plate to housing and remove brake assembly. Support brake assembly to prevent injury to the brake cable.
4. Remove outer oil seal and roller bearing, then remove inner oil seal, using Remover  J1436. See figure 5-6.

1951 Buick Removing Wheel Bearing and Oil Seal

Installation of Axle Shaft

1951 Buick rear axle shafts are not interchangeable between sides because the right hand shaft is longer than the left.

1. Fill rear wheel bearing and space between oil seals with wheel bearing lubricant. Coat leather edges of oil seals with lubricant.
2. Support axle shaft as it is inserted into 1951 Buick rear axle housing to avoid damaging wheel bearing oil seals.
3. Push axle shaft in as far as possible, install horseshoe-shaped lock washer in groove in inner end of shaft, then pull shaft out to seat lock washer in recess in differential side gear.
4. Install differential spacer between ends of axle shafts and with both shafts pulled outward as far as possible, check clearance between spacer and shafts with feeler gauges. Total clearance, or axle shaft end play, should be between .000″ and .008″.
5. If clearance exceeds .008″, turn spacer 1/4 turn and test clearance again; the spacer has two different thicknesses to permit a selective fit.
6. If clearance or axle shaft end play cannot be adjusted to .008″- or less with old spacer, install a new spacer. Service spacers are oversize to permit some take up for wear.
7. In some cases, however, it may not be possible to adjust end play to specified limits by installation of oversize spacers; therefore, new bronze thrust washers should be installed between the differential case and the side gears before selecting a spacer of proper thickness to provide not over .008″ end play.
8. After proper axle shaft end play is obtained, place side pinions and thrust washers in case and push differential side pinion shaft through case, thrust washers, and pinions. Lock shaft in place with lock screw and lock washer.
9. Pour a liberal quantity of rear axle lubricant on gears and bearings, and turn rear wheels to work lubricant into all surfaces.
10. Install housing cover, using new gasket and coating bolt threads with white lead to avoid oil leaks. Align filler plug with first bolt hole to right of lower center bolt hole in housing. This change from straight down position increases oil level to 4 pints.
11. Install brake drum and rear wheel. If brake backing plate was removed for bearing replacement (subpar. b), bleed brake wheel cylinder as described in paragraph 8-9.
12. Remove car stands so that car is level, then fill housing to filler plug opening with factory hypoid gear lubricant (Group 5.535) and install filler plug securely.

5-10 REMOVAL OF RING GEAR AND CASE, PROPELLER SHAFT AND PINION ASSEMBLIES

NOTE: On all Dynaflow Drive cars and Synchromesh cars equipped with the 3.6 or 3.9 rear axle gear ratio it is necessary to remove the 1951 Buick rear axle assembly (par. 5-8) in order to remove the propeller shaft and pinion. This is not necessary on Synchromesh cars having the 4.1 gear ratio because a pinion puller is available, and the propeller shaft spline seal is not used.

Removal of Ring Gear and Case Assembly

1. After removal of both axle shafts (par. 5-9), remove differential side gears and thrust washers from case to prevent them falling out and being damaged.
2. If ring and pinion gear set has been operating quietly and is to be reinstalled, it is advisable to wash lubricant from between gear teeth and check existing gear lash by means of dial indicator, so that the same lash can be used when parts are reinstalled, to avoid changing gear tooth contact. See paragraph 5-16, steps Sand 9.
3. CAUTION: Backlash will be reduced when pinion is locked by prying up with a bar if there is excessive pinion lift due to worn bearings. See subparagraph b, step 2, below.
4. Mark the differential bearing caps so they can be reinstalled in original positions on the carrier. Interchanging the caps will cause damaged threads because caps are threaded in production while bolted to carrier.
5. Remove bearing adjuster locks, loosen one adjuster, support the differential gear and case assembly while removing bearing caps and adjusters, then lift differential assembly and bearing races out of carrier.
6. See paragraphs 5-11 and 5-16 for inspection and installation procedures.

Removal and Disassembly of Propeller Shaft and Pinion Assembly

1. If ring and pinion gear set has been operating quietly and is to be reinstalled, it is advisable to check the pinion setting after removal of differential case so that the same setting can be used when parts are reinstalled to avoid changing gear tooth contact. See paragraph 5-15.
2. At this point it may be desirable to test pinion shaft bearing wear without removing pinion shaft. Install 1 1/4″ extension on stem of dial indicator and mount indicator to bear down against center drilling in pinion gear, with indicator stem as near vertical as possible. See figure 5-7.

1951 Buick Testing Pinion Bearing Wear

Pry up on pinion gear with bar a number of times while observing indicator reading. A reading in excess of .0015″ indicates that bearing is worn enough to produce noisy gear operation.

1951 Buick Pinion Puller

This puller will not fit over the pinions of the 3.6 and 3.9 gear sets; therefore, in those jobs the parts must be removed by tapping on the front end of propeller shaft, using a babbit hammer, brass bar, or a protective cap to avoid damaging shaft.

1951 Buick Pinion Press J 1292-B

5-11 CLEANING AND INSPECTION OF 1951 BUICK REAR AXLE PARTS

Cleaning 1951 Buick Rear Axle Parts

Hypoid lubricant is extremely allergic to water and when contaminated with even small quantities of water it has a deteriorating effect on the lubricant. For this reason steam or water should not be used for flushing 1951 Buick rear axle assemblies. If used on 1951 Buick rear axle parts which are disassembled, extreme care must be used to thoroughly dry all parts before installation.

Gasoline, kerosene, or other distillates are satisfactory for cleaning parts when removed from rear axle housing, if parts are thoroughly dried before installation. They should not be used in an assembled rear axle, however, because if all traces of the cleaner are not removed the fresh lubricant will be contaminated. For this reason, only SAE 10-W or flushing oil is recommended for flushing and cleaning an assembled 1951 Buick rear axle.

Wash all parts in clean solvent and wipe dry with clean cloths. Thoroughly wash out interior of 1951 Buick rear axle and third member housings and wipe dry with clean cloths. Blow out all dirt with clean, dry air stream.

Inspection of 1951 Buick Rear Axle Parts

1. Thoroughly inspect all bearings as described under Bearing Service (par. 1-12). Be particularly careful to inspect rear wheel bearings, including inner race on axle shafts, for corrosion caused by rust and for flat Spots on rollers.
2. Carefully inspect all gears for scores on face of teeth, for chipped teeth and for excessive wear. Examine ring gear and pinion for improper tooth contact. See figure 5-2.
3. Pinion and Propeller Shaft. Check for wear of splines on pinion and in the propeller shaft. Pinion must be tight fit in propeller shaft when parts are assembled. Inspect interior of propeller shaft and if oil is present wash it out thoroughly and dry interior with air.
4. 1951 Buick Rear Axle and Third Member Housings. A sprung housing should be replaced- ; straightening is not recommended. A housing must never be heated with a torch as this may produce soft spots in the metal in which fatigue and breakage may develop in service.

Inspect third member housing for: oil leak at torque ball and at flanged joint between torque tube and carrier; cracked torque tube; strut rod brackets broken or cracked at welds; pinion shaft bearing bores galled or worn due to bearing turning in housing; stripped or damaged threads in side bearing pedestals or caps. See paragraph 5-13 for replacement of housing.

Checking Pinion and Rear Bearing Clearance

The desired clearance between pinion and the rear (roller) bearing is .0005″. The maximum allowable clearance for quiet operation is .0014″. Excessive clearance at this point is usually caused by wear of the roller bearing.

Wear of the roller bearing may be checked with a micrometer. Before checking, make certain that bearing is absolutely clean and that micrometer is accurate at zero reading. Measure across the outer race and a roller at four or five points around bearing as shown in figure 5-10, using care to adjust micrometer lightly to high points of roller and race to insure an accurate reading.

1951 Buick Checking Wear of Pinion Rear Bearing

The micrometer will read .6756″ to .676″ if bearing is satisfactory for use. If reading is less than .6756″ the bearing is worn and should be discarded.

An alternate method of checking clearance between pinion and roller bearing is shown in figure 5-11.

1951 Buick Checking Clearance Between Pinion and Roller Bearing

Obtain a piece of tough paper, such as typewriter “second” sheet which measures .0015″ thick (use micrometer) and cut a test strip 3/16″ wide. Place bearing on pinion about 1/4”’ above spacer, insert .paper test strip between two bearing rollers and rotate bearing until strip is under one roller. If clearance is satisfactory, the bearing will hang on the paper strip and the paper strip cannot be pulled out. If bearing drops of its own weight, or paper strip can be easily pulled out, the clearance is excessive and bearing should be discarded.

NOTE: If roller bearing is worn excessively, it is quite likely that the double-row front bearing is worn so that it no longer has any preload. Inspect this bearing very carefully and discard if loo se or doubtful.

5-12 REPLACEMENT OF RING GEAR, DIFFERENTIAL CASE, OR BEARINGS

Ring gears are furnished for replacement only with the pinions in matched sets. Ring and pinion gear sets and differential cases are furnished separately and also with the ring gear riveted to the case. If case or gear set is satisfactory it should not be discarded because the other part requires replacement.

Replacement of Ring Gear or Differential Case

1. Center punch all rivet heads on ring gear side, placing marks in center of heads. Drill rivets approximately 1/2″ deep with 1/4″ drill. See figure 5-12.

1951 Buick Checking Run-out of Ring Gear

Replacement of Differential Bearings

1. If a differential bearing is to be replaced, or removed from old differential case and installed on new case, pull bearing from case using Bearing Puller J 2241. See figure 5-16. The ends of puller jaws fit into notches in differential case so that pressure can be applied to bearing inner race. Do not pull on rollers.

1951 Buick Installing Differential Bearing Using Replacer J 2242

5-13 REPLACEMENT OF THIRD MEMBER HOUSING

The third member housing consists of the torque tube and differential carrier which are flanged and bolted together. The bolted construction is for manufacturing purposes only; torque tube and carrier are not furnished separately for service.

The torque tube and carrier are matched and aligned during manufacture and always must be kept in their original assembly. The tube and carrier should never be disassembled unless it is necessary to install a new gasket to correct an oil leak. The gasket is of special material and substitute material should not be used.

When removing a third member housing, after removal of 1951 Buick rear axle assembly from car, drill through the heads of strut rod attaching rivets with a 7/16″ drill. If rivet heads are cut off with hammer and chisel without drilling, the holes in strut rods and brackets will be distorted.

Third member housings furnished for service replacement are not drilled for rivets in the strut rod bracket. The holes must be drilled after the 1951 Buick rear axle housing, third member housing, and strut rods are assembled together. With strut rods in normal position and without up or down strain, drill bracket to match holes in strut rods with 1/2″ drill. Drill through strut rods and bracket with a 9/16″ drill, then install bolts No. 1312923 with 1/8″ lock washers and thin nuts.

5-14 ASSEMBLY AND STRAIGHTENING OF PINION AND PROPELLER SHAFT

Installation of Pinion Bearing Oil Seal – If Required

In cases where oil seeps from the 1951 Buick rear axle into the torque tube or propeller shaft and may pass a defective propeller shaft spline oil seal and enter the transmission, correction may be affected by installation of a pinion bearing oil seal. The oil seal and a special pinion bearing lock nut is furnished in a kit for service installation under Group 5.445.

The differential carrier is bored to proper size for the seal so that it is not necessary to fit the seal into the carrier bore. Install the seal on the special pinion bearing lock nut with the inner leather seal pointing away from hex of nut. See figure 5-18. Assemble pinion and propeller shaft with these new parts as described below (subpar. b).

1951 Buick Pinion Bearing Oil Seal

Assembly of Pinion and Propeller Shaft

NOTE: Before assembly make certain that interior of propeller shaft is free of oil and is clean and dry. Any foreign material in propeller shaft will throw it out of balance and cause vibration.

1. Install parts on pinion shaft in the following order: rear bearing spacer, two rear bearings (roller), bearing lock sleeve with thick end toward spline, front bearing (ball) with shielded side toward spline. See figure 5-19.

1951 Buick Gear Set with Bearings and Lock Sleeve

Press front bearing solidly against shoulder on pinion shaft, using a tube of proper size to bear against inner race only. NOTE: Bearing may be brinnelled if driven into place.

IMPORTANT: Whenever a pinion and propeller shaft are assembled together the complete assembly must be checked for straightness regardless of whether new or original parts are assembled. See following subparagraphs.

Straightening Pinion and Propeller Shaft Assembly, Using Fixture

The pinion and propeller shaft assembly may be quickly and satisfactorily checked and straightened by means of the fixture shown in figure 5-20.

1951 Buick Checking Propeller Shaft in Fixture

This fixture should be made locally, using a 1949 or 1950 differential carrier. A special N.P.N. carrier (without torque tube) may be ordered for this purpose from the Buick Service Department, Flint, Michigan. Details of the carrier supports are given in B.P.S. 2.214 and in figure 5-20 of the 1948-49 Buick Shop Manual.

1. Mount the pinion and propeller shaft assembly in the fixture, being sure to tighten pinion bearing lock screws evenly and securely to press pinion front bearing solidly against shoulder.
2. Mount a dial indicator on a rod fastened to a block of sufficient weight to hold the indicator button firmly against the ground portion of the propeller shaft, just to the rear of the splines as shown in figure 5-20.
3. Turn the shaft by hand from the pinion end and note the amount of run-out as shown by the indicator. The total indicator reading should not exceed .015″.
4. If the reading exceeds .015″, turn shaft to high point on indicator and force end of shaft downward by hand sufficiently to spring it to within .015″ run-out. Recheck for run-out after each springing operation.

Straightening Pinion and Propeller Shaft Assembly, Using V-Blocks

If the fixture shown in figure 5-20 is not available, the pinion and propeller shaft may be checked and straightened using V-blocks or rollers and a dial indicator.

1. Support the assembly on V-blocks placed under the machined section just to rear of splines at “A” and under the rear (roller) bearing at “B”. See figure 5-21.

1951 Buick Propeller Shaft Run-out Specifications

5-15 INSTALLATION AND ADJUSTMENT OF PINION AND PROPELLER SHAFT

Installation of Pinion and Propeller Shaft

Before installation of pinion and propeller shaft assembly make certain that interior of 1951 Buick rear axle and third member housing s are absolutely clean and dry. Al so make certain that parts to be installed are clean and that pinion bearing shims are not damaged.

1. If the original third member housing and pinion shaft are being used, place the original number and thicknesses of pinion bearing shims over propeller shaft against front bearing, to maintain original setting of pinion.
2. If a new pinion is being installed, change the total thickness of shims by the difference between the old pinion and new pinion setting marks as explained in subparagraph b, below. For example: if old pinion is marked “+3” (plus3) and new pinion is marked “-2″ (minus 2), total thickness of shims installed should be .005” greater than shims removed.

NOTE: Shims furnished with new gear sets are for use as required in adjustment and are not necessarily of correct total thickness.

3. Lubricate both pinion bearings thoroughly with 1951 Buick rear axle lubricant which should also be used to hold shims against front bearing. As pinion and propeller shaft assembly is inserted into third member housing, turn pinion front bearing outer race so that the ball loading groove will be straight up, to prevent oil running through into torque tube.
4. As the pinion rear bearing enters third member housing, place Pinion Bearing Spacer J-1192-B, (1/4″ thick) between bearing and pinion gear so that bearing can be pushed into place without binding against spacer on pinion shaft. See figure 5-22.

1951 Buick Use of Pinion Bearing Spacer J 1192-B

Pinion Setting Marks and Setting Gauges

All Buick ring and pinion gear sets are selectively matched for quiet operation and proper tooth contact. After matching, a serial number is etched on one tooth of pinion and on rear face of gear to aid in keeping matched parts together. See figure 5-23. Parts having different matching serial numbers must never be used together.

1951 Buick Ring and Pinion Gear Markings

Ring and pinion gear sets are matched in a special test machine which permits adjustment of pinion depth in ring gear until a point is reached where quiet operation and proper tooth contact under load is obtained. At this point, the setting of pinion with reference to centerline of ring gear is indicated by the machine. This setting may vary a few thousands of an inch from the design or “nominal” setting due to allowable variation in machining the parts.

In order to make it possible to duplicate the matching setting of the pinion when the gear set is installed in a third member housing, the pinion is marked to indicate this setting with reference to the “nominal” setting. The amount of thousands of an inch plus or minus the “nominal” setting is etched on the small end of one pinion tooth. See figure 5-23. When a pinion is marked “+” (plus) it means that the pinion must be set at a distance from the centerline of the ring gear equal to the “nominal” setting plus the amount indicated on pinion tooth. When a pinion is marked”-” (minus) it means that the pinion must be set at a distance equal to the “nominal” setting minus the amount indicated on pinion tooth.

Nominal micrometer reading “nominal” setting minus the amount indicated on pinion tooth.

Pinion Setting Gauge J 681-A or J 2197 is required in order to measure the pinion setting after- it is installed in a third member housing.

Pinion Setting Gauges J 681-A and J 2197 are identical except for the markings of the micrometer section, as described below. Either tool consists of a micrometer gauge, a checking gauge, an adapter for use with hypoid gear sets, and a clamp to hold the adapter in position. The micrometer gauge has sliding stepped collars so that gauge can be used in all models. The checking gauge should be used to test the accuracy at zero of the micrometer gauge before using the gauge. See figure 5-24.

1951 Buick Pinion Setting Gauge

Pinion Setting Gauge J 681 A

This gauge has the thimble and sleeve of the micrometer marked exactly like a standard micrometer. See figure 5-26. When the thimble is turned clockwise to extend the spindle, the reading becomes less. Consequently, when this gauge is used to measure depth of a pinion marked “+” (plus), the amount marked on the pinion tooth must be subtracted from the “nominal” micrometer reading. Likewise, if pinion is marked “-” (minus), the amount marked on the pinion tooth must be added to the “nominal” micrometer reading.

Example:

1951 Buick Pinion Setting Gauge J 681 A

Pinion Setting Gauge J 2197

This gauge has the thimble and sleeve of the micrometer marked the opposite of a standard micrometer. See figure 5-26. When the thimble is turned clockwise to extend the spindle, the reading becomes greater. Consequently, when this gauge is used to measure depth of a pinion marked “+” (plus) the amount marked on the pinion tooth must be added to the “nominal” micrometer reading. Likewise, if pinion is marked “-” (minus), the amount marked on the pinion tooth must be subtracted from the “nominal” micrometer reading.

Example:

1951 Buick Pinion Setting Gauge J 2197

Checking Pinion Setting with Gauge

1. Before Pinion Setting Gauge is installed, check the ends of pinion teeth and stone off any burrs; also rub stone over etched markings to remove high spots. The gauge adapter must seat flatly and firmly against ends of pinion teeth in order to secure an accurate micrometer reading.
2. Install adapter with clamp, and the micrometer gauge as shown in figure 5-25.

1951 Buick Pinion Setting Gauge Installed

The adapter must be firmly held against the pinion by the clamp. The micrometer gauge must be firmly seated in the differential bearing seats in carrier, with micrometer spindle at 90 degrees to surface of adapter.

If the ring and pinion gear set is new, or has not been in use long enough to establish a wear pattern on teeth, the micrometer reading should be within .001″ (plus or minus) of the reading given under the proper pinion marking in figure 5-26. Note that figure 5-26 gives one pinion setting table for Gauge J-681-A and another for Gauge J 2197 since the micrometers are not marked alike on both gauges.

1951 Buick Pinion Setting Tables for Gauge J 681-A and Gauge J 2197

5. If pinion setting is not as specified, adjust as described below.

Adjustment of Pinion

The pinion setting is adjusted by changing the total thickness of the pinion bearing shims which are located between the pinion front bearing and the shoulder in third member housing.

1. Remove pinion and propeller shaft assembly (par. 5-10, b).
2. Remove all pinion bearing shims from shaft or in third member housing, wipe shims dry, and measure their total thickness with a micrometer, or with a dial indicator set to bear against a flat surface.
3. Increase or decrease total thickness of shims as required to obtain proper pinion setting, by using a different combination of shims. These shims are furnished in thicknesses ranging from .010″ to .019″ in increments of .001″, so that any total thickness may be obtained by using a combination of different shims.
4. Install pinion and propeller shaft assembly with new combination of shims and be sure to tighten the three bearing sleeve locks uniformly to 35-40 ft. lbs. torque, and lock nuts to 15-20 ft. lbs. torque.
5. Check pinion setting with gauge. Setting should be within .001″ plus or minus, of required micrometer reading.

5-16 INSTALLATION AND ADJUSTMENT OF RING GEAR AND CASE ASSEMBLY

1. Before installation of ring gear and case assembly make sure that differential bearing seats in carrier pedestals and caps are clean and free of burrs. Remove any burrs which might prevent bearings or bearing caps from seating properly.
2. Place outer races on differential bearings but do not oil bearings as this would interfere with bearing adjustment. Install gear and case assembly in carrier and slide bearing adjusters into position so that threads are engaged in threads in carrier pedestal.
3. Install bearing caps with bolts, making sure that caps are installed in original positions as marked before removal. Turn bearing adjusters to engage threads in caps. Tighten cap bolts to 20 ft. lbs. torque then loosen all four bolts 1/4 turn.
4. Using Adjuster Wrench J 1365 (fig. 5-27) turn adjusters as required to set ring gear lash at approximately .008″ to .012″, with both adjusters in firm contact with bearings.

1951 Buick Adjusting Differential Bearings

CAUTION: Do not use punch and hammer to turn adjusters as adjusters will be distorted and proper bearing adjustment cannot be obtained.

1951 Buick Checking Back Lash with Dial Indicator

Use a small button on indicator stem so that contact can be made off the edge of tooth. Set dial indicator so that indicator stem is as nearly in line with gear rotation as possible. If stem bears against edge of tooth, or stem is at considerable angle to the line of gear rotation, a false indication of backlash will be obtained.

1951 Buick Differential Side Gears, Pinions, and Thrust Washers

IMPORTANT-Break-in with New Gears
When new gears are installed in a 1951 Buick rear axle assembly by the dealer, the car owner must be cautioned to operate the car in the same manner as he would a new car, for a reasonable length of time until the new gears have run in smoothly.

New gears may be scored during break-in by sustained high speed driving, harsh use of clutch causing rear wheels to spin, and by coasting at high speed with clutch disengaged and engaging clutch suddenly.