Complete bearing, race, shim and seal kit for rebuilding or re-gearing the GM 8.875 inch 12-bolt passenger car rear end (Chevelle, Camaro, Nova, Impala).
The 8.875 inch GM 12-bolt car rear end is the muscle-car axle under 1960s and early-1970s Chevelles, Camaros, Novas, Impalas and their cousins, and most of them are now carrying 50-plus years of bearing wear. If yours howls on the highway, clunks when you get into the throttle, or you are about to install a new ratio or posi unit, the Yukon YK GM12P master overhaul kit gives you every bearing, race, shim and seal the center section needs so the rebuild starts from known parts.
The 12-bolt car rear uses an 8.875 inch ring gear driven by a hypoid pinion on two tapered roller bearings, with a crush sleeve holding pinion preload. A shim under the inner pinion bearing sets pinion depth. The carrier rides on two tapered bearings, and the 12-bolt sets backlash and carrier preload with shims between the bearing and the case, the classic GM layout that makes a full shim assortment essential.
According to Yukon, the kit includes carrier bearings and races, pinion bearings and races, the pinion seal, a complete shim kit, ring gear bolts, pinion nut, crush sleeve, thread locker, marking compound with a brush, and the cover gasket, with Timken bearings and races. Gears, carrier and axle bearings are not in the box.
Confirm it is a real car 12-bolt first. Count twelve cover bolts, then check the year and the stamped code on the right axle tube; a 12-bolt under a 1999-and-later GM truck is a completely different 9.5 or 9.76 inch axle. Our 10-bolt vs 12-bolt guide covers the identification. Then grab the pinion yoke and push it in and out; any clunk means the pinion bearings have lost preload. Use the whine diagnosis guide to separate gear noise from bearing noise, and paint the ring gear to see whether the teeth are pitted. Damaged teeth mean new gears, such as the 12-bolt car 3.73 ring and pinion, on top of this kit, or a 3.90 12-bolt car gear set if you want a steeper ratio.
This kit fits the GM 8.875 inch 12-bolt passenger car differential. It does not fit the 12-bolt truck axle from 1960s and early-1970s half-ton pickups; Yukon sells a separate truck kit, YK GM12T, and the car and truck gears are not interchangeable either. It also does not fit the 8.2 or 8.5 10-bolt that went under many of the same body styles. Rear ends get swapped constantly in these cars, so identify the axle in the car rather than trusting the build sheet. If you are unsure, send us the axle tube code or the year and VIN and we will confirm. More kits are in our rebuild kits section.
Follow the order Yukon publishes: pinion depth, then pinion bearing preload, then backlash, then carrier bearing preload. Yukon's chart for the 12-bolt passenger axle lists 14 to 19 in-lb of pinion preload with new bearings (6 to 9 in-lb on used), 0.006 to 0.011 inch of backlash, 55 ft-lb on the ring gear bolts and 60 ft-lb on the carrier caps. Set pinion depth and check the pattern before you collapse the crush sleeve, because a sleeve crushed too far has to be replaced. Our backlash and pinion depth setup guide shows how to read the marking compound. If the posi is slipping, now is the time to replace it with a Dura Grip positraction for the 12-bolt car while the carrier is out. Fill with 75W-90 GL-5 gear oil and add friction modifier for a clutch-type posi. Break new gears in gently: Yukon recommends letting the axle cool after the first 15 to 20 miles.
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No. The car and truck 12-bolts both use an 8.875 inch ring gear, but the bearings and pinion differ. Yukon sells a separate YK GM12T kit for the truck axle.
No. The 12-bolt on 1999-and-later GM trucks and SUVs is the 9.5 or 9.76 inch axle, a different design that needs its own kit. This kit is only for the classic 8.875 inch car 12-bolt.
Yes. Yukon lists ring gear bolts in the GM12P kit, along with thread locker. Its setup chart calls for 55 ft-lb on the 12-bolt passenger ring gear bolts.
Yes, if the teeth are not pitted, chipped or scored. Record the old shim stack and contact pattern before teardown, then use the new shims to bring pinion depth and backlash back into spec.
A 75W-90 GL-5 gear oil. Add friction modifier if the axle has a clutch-type posi. Change the oil after the break-in miles to remove early wear metal.
