For 1990-2009 cars

# Info - 2-Cut vs. 5-Cut Rear Axle Ring and Pinion Gearsets

Subject: | 2-Cut vs. 5-Cut Rear Axle Ring and Pinion Gearsets

Models: | 2002 and Prior Chevrolet and GMC Light Duty Truck Models

| 1999-2000 Cadillac Escalade

| 2002 Cadillac Escalade

| With 8.6 Inch Ring Gear (3.08, 3.42, 3.73 or 4.10 Ratio) Rear Axles

This bulletin is being revised to add model, parts and text information. Please discard Corporate Bulletin Number 00-04-20-001 (Section 04 -- Driveline/Axle).

The purpose of this bulletin is to inform technicians of the difference between a 2-cut and a 5-cut ring and pinion gearset pattern (manufacturing process only). Current technical publications are for 5-cut gearsets. However, both 2-cut and 5-cut gearsets are available in service and production.

Technicians report that they are unable to properly set the ring and pinion and get the same pattern as the gear that was removed. After the vehicle was driven, the vehicle exhibited severe rear axle noise from trying to match the pattern of a 5-cut gearset.

The 2-cut gearsets meet all manufacturing specifications and should be considered quality gearsets. The "set-up" condition stated above might have been the result of one of the two following possibilities:

• | The technician is trying to make a 2-cut gearset pattern conform to the same build pattern as a 5-cut gearset. Because of the manufacturing differences, the build pattern on 2-cut and 5-cut gearsets is significantly different. The most accurate way to tell the difference between a 2-cut and a 5-cut gearset is to look at the toe to heel tooth height of the ring gear.

#### 2-Cut Drive Side (Natural Bias Pattern)

• | The 2-cut gearsets have a natural "bias" condition in the patterns. Bias shows as a slanted pattern (1) on the gearset when rolled with marking compound. On a 2-cut gearset, the height of the tooth remains constant from the tooth's toe to heel. When attempting to turn a biased pattern into a square pattern by altering the pinion shim thickness and/or backlash, a 2-cut gearset will become noisy.

#### 5-Cut Drive Side (Rectangular Pattern)

• | The 5-cut gearsets show as a "no-bias" or "square" pattern (1) when rolled with marking compound. On a 5-cut gearset, the height of the tooth increases from the tooth's toe to heel.

• | The technician is attempting to adjust the gearset contact pattern by changing only the pinion shim thickness instead of changing the backlash of the gearset.

| Generally, changing the pinion shim thickness will cause the gearset contact pattern to move either from the face side to the flank side of the tooth or from the flank side to the face side of the tooth. Toe-to-heel and heel-to-toe gearset pattern adjustments can generally be accomplished by changing the amount of backlash that is between the drive pinion and the ring gear.

| Both gearsets use the same procedure to adjust the backlash. Refer to the Rear Drive Axle sub-section of the Service Manual for procedures on adjusting backlash.

Important: The pinion nut and washer should be replaced whenever the ring and pinion is serviced. Before the nut is removed, verify the rolling resistance. Refer to the Rear Drive Axle sub-section of the Service Manual for further information.

### Parts Information

Two-cut ring gear kits are now available. The 2-cut gear kit(s) includes a gear set, a pinion spacer (crush sleeve), and ten cover bolts. The kit(s) does not include a pinion nut and washer.

At the time of this publication, the 3.08 inch axle ratio gear set is NOT available from GMSPO. This bulletin will be revised when the kit becomes available.

Part Number | Description
--- | ---
12479129 | Gear Set, Diff Ring & Drv Pinion (3.42 Axle Ratio)
12471280 | Gear Set, Diff Ring & Drv Pinion (3.73 Axle Ratio)
12479056 | Gear Set, Diff Ring & Drv Pinion (4.10 Axle Ratio)
88891763 (Pack of 5) | Nut, Prop Shft Pin Flg
517900 | Washer, Pinion

Parts are currently available from GMSPO.