Drive Pinion Shim Selection

Individual differences in machining the carrier casting and the gear set and variation in bearing widths require a shim between the pinion rear bearing and pinion head, in order to locate the pinion for correct tooth contact with the ring gear.

Checking Pinion Depth:

When replacing a ring and pinion gear, the correct shim thickness for the new gear set to be installed is determined by the following procedure using Pinion Depth Gauge T79P-4020-A.

1. Assemble the appropriate aligning adapter, gauge disc and gauge block to the screw.

Pinion Gauge Block:

2. Place the rear pinion bearing (new, or used if in good condition) over the aligning tool and insert it into the rear pinion bearing cup of the carrier. Place the front bearing into the front bearing cup and assemble the tool handle into the screw (refer to illustration in Step 4). Roll the assembly back and forth a few times to seat the bearings while tightening the tool handle by hand. Tighten the tool handle to 27 Nm (20 ft-lbs).

NOTE: The gauge block must be offset (45°) to obtain an accurate reading.

Measuring Correct Pinion Shim Thickness:

3. Center the gauge tube into the differential bearing bore. Install the bearing caps and tighten the bolts to 95-115 Nm (70-85 ft-lbs). (Caps are to be installed with the triangles pointing outboard.)

Utilize PINION SHIMS as the gauge for shim selection. This will minimize errors in attempting to stack feeler gauge stock together or simple addition errors in calculating correct shim thickness.

NOTE: Shims must be flat. Do not use dirty, bent, nicked or mutilated shims as a gauge.

It is important to feel a slight drag on the shim for correct selection. Do not attempt to force the shim between the gauge block and the gauge tube. This will minimize selection of a shim thicker than required, which results in a deep tooth contact in final assembly of integral axles.

4. Place the selected shim(s) on the pinion and press the pinion bearing cone and roller assembly until it is firmly seated on the shaft.

NOTE: The same rear pinion bearing used in this procedure must be used in final assembly of the axle.

Assembling Pinion Gear And Bearing Assembly:

NOTE: Be sure that press load is not applied to the bearing cage.