GM 12-Bolt Truck Ring and Pinion Install Kit, Allstar ALL68518

Old Chevy and GMC half-ton pickups and K5 Blazers with the 12-bolt truck rear are favorites for restomods and lifted builds, and almost every one of them needs bearings by now. If yours howls at highway speed, clunks when you get on and off the gas, or you are putting in a new ratio, the Allstar Performance ALL68518 ring and pinion installation kit carries the bearings and hardware for the 8.875 inch GM 12-bolt truck axle.

What the install kit does in a GM 12-bolt truck rear

The truck 12-bolt shares the 8.875 inch ring gear size with the Chevelle and Camaro 12-bolt, but the inside is different. Allstar's own chart lists ALL68518 for the Chevy and GMC truck and Blazer axle with a 1.438 inch pinion, and a separate kit, ALL68519, for the passenger car axle with a 1.625 inch pinion. That pinion bearing size is why the two kits do not interchange.

The pinion rides on two tapered bearings held in preload by a crush sleeve and pinion nut, and the carrier rides on two side bearings set by shims. Allstar lists its bearing kits as including pinion and side bearings, pinion seal, pinion depth shims, adjustable side shims, crush sleeve or solid spacer, pinion nut, a one-ounce tube of silicone or gasket, gear marking compound and ring gear bolts, with the note that components vary by application. The listing for this truck kit names a crush sleeve and silicone.

Symptoms that call for this kit

• A whine that rises with road speed and changes between acceleration and coast
• A growl that gets louder with a load in the bed or a trailer hooked up
• Clunk at the driveshaft on and off throttle, or play at the pinion yoke
• Gear oil on the yoke and crossmember from a leaking pinion seal
• Any regear for bigger tires or a highway ratio, since new gears should never run on old bearings

How to confirm before ordering

First confirm you have a truck 12-bolt and not a 10-bolt or the car 12-bolt. Count the cover bolts, then look at the cover shape and the axle code. Our GM 10-bolt vs 12-bolt guide and the axle code and ratio guide walk through the identification. With the driveshaft off, turn the pinion by hand: a gritty feel or in-and-out play means the pinion bearings are worn.

Fitment

This kit is listed for the GM 12-bolt truck rear with the 8.875 inch ring gear in 1964-1982 Chevrolet and GMC trucks and Blazers. It does not fit the 12-bolt passenger car axle, the 8.5 inch 10-bolt, or the later 9.5 inch 14-bolt or 2014-up 9.5 inch 12-bolt. Early trucks had spline and housing variations, so check your pinion and housing, or send us your year and VIN before ordering. For the car axle, the Yukon 12-bolt car overhaul kit is the match. More kits are in our rebuild kits category.

Install notes

• Pull the cross-pin and C-clips before the axles and carrier come out, and mark the bearing caps left and right
• Measure the old pinion shim and use it as a starting point for depth
• Seat new races fully with a bearing race and seal driver set
• Tighten the pinion nut in small steps against the new crush sleeve and check turning torque; overshoot it and the sleeve must be replaced
• Shim the carrier for backlash and side preload, then paint the ring gear with the marking compound and read both drive and coast sides, as in our backlash and pinion depth setup guide
• Fill with 75W-90 gear oil, adding friction modifier for a limited slip

If the ratio is changing, the Yukon 12-bolt truck 3.73 gear set installs with this kit. A fresh 12-bolt truck cover is worth it if the old one is bent at the gasket face. Break new gears in with the break-in procedure before towing.

Will ALL68518 fit a Chevelle or Camaro 12-bolt?

No. Allstar lists ALL68518 for the truck and Blazer 12-bolt with a 1.438 inch pinion. The passenger car 12-bolt uses a 1.625 inch pinion and Allstar kit ALL68519.

What is included in the kit?

Per the listing, pinion and carrier bearings, pinion seal, pinion depth shims, carrier shims, crush sleeve, pinion nut, silicone and gear marking compound. Allstar notes components can vary by application.

Which years does it fit?

It is listed for the GM 12-bolt truck rear in 1964-1982 Chevy and GMC trucks and Blazers. Confirm the axle by the cover and axle code, or send us your year and VIN.

Do I need new gears to use this kit?

No. It works as a bearing overhaul with the original gears if the teeth are clean. If you are changing ratio, install the new gears and this kit at the same time.

What gear oil goes in the 12-bolt truck rear?

75W-90 gear oil, with friction modifier if it has a limited slip carrier. Change it after the break-in miles on new gears.