6-1 SPECIFICATIONS

  1. Rear Axle Gear Ratios

The following gear ratios are standard; optional gear ratios are not available. The gear ratio is indicated by numbers stamped on bottom of axle housing.

1955 Buick Rear Axle Gear Ratios

1955 Buick Rear Axle Gear Ratios

6-2 CHANGES

  1. Description

The 1955 Rear Axle Assembly is the same design previously used; however the pinion bearings which support the pinion in the differential carrier have been changed to provide longer life and greater load carrying ability.

The new assembly consists of one Hyatt roller bearing (rear) and one New Departure double row radial thrust ball bearing (front) , with a longer lock sleeve and wider spacer to compensate for the elimination of one rear bearing. See figure 6-1.

1955 Buick Pinion and Related Parts

1955 Buick Pinion and Related Parts

The new double row thrust bearing has no shield, therefore, the oil seal has been redesigned for installation with the new bearing.

The ring gear is now bolted to the differential case instead of being riveted as in past models, providing a tighter and better fit of the mating parts. Special 3/8″ x 24, 300M bolts are threaded into tapped holes in the ring gear after passing through the differential case. (Lock washers are not used.) These bolts are constructed of a heat treated metal which gives them increased tensile strength characteristics, and should not be replaced by any other kind of a 3/8″ x 24 bolts under any circumstances.

When replacing a bolted type ring gear to the differential case, the bolts should be tightened in a sequence opposite to each other, to 35Ft. Lbs. the first time around, then finally to 50 to 60 Ft. Lbs. “Run-out” of the differential case flange and the ring gear are checked the same as in 1954. See 1954 Shop Manual, Par. 6-9a.

NOTE: The new bolted ring gears are not interchangeable with the riveted type.

  1. Service Information
  1. No change in pinion setting and location.
  2. The new oil seal (Part No. 1339437) must be used with new bearing (Part No. 954919) or interference on the nut hex may result. The ball bearing (Part No. 954919) has no shield, therefore it is not recommended for earlier jobs not using the pinion oil seal.
  3. If the new bearing arrangement (with one rear roller bearing) is to be installed in a rear axle in which the old arrangement (two rear roller bearings) has previously been run, a new gear set MUST also be used.
  4. The double row bearing is installed with the ball loading groove toward the spacer.
  5. A new pinion bearing spacer (J-5905) is used to press the pinion gear into the carrier. The new tool consists of two pieces; a spacer similar to the 1954 tool with a handle, and an additional spacer with a chain attached. When positioning the tool for use, the spacer with handle is positioned next to the bearing while the additional spacer (with chain attached ) is positioned next to the pinion. See figure 6-2.
1955 Buick Pressing Pinion and Shaft Into Place

1955 Buick Pressing Pinion and Shaft Into Place

Following the pressing of the pinion into place, the chain may be used to pull one part of the spacer out, leaving sufficient space to remove the balance of the tool.

NOTE: The spacer tool applies the assembling force by way of the outer races of the bearings so that undue force is not exerted on the balls of the front bearing which results in damage and noisy bearings.

  1. Parts Comparison

Part numbers for the 1954 and 1955 rear axle groups are shown in the following table:

1955 Buick Rear Axle Parts Comparison

1955 Buick Rear Axle Parts Comparison