GM 8.6 IRS Rear Differential Master Bearing Kit, Koyo

This is the Motive Gear R8.6RMK master bearing kit for the GM 8.6-inch independent rear (IRS) differential. It does not fit the ZL1 rear. The kit uses Koyo tapered carrier and pinion bearings and includes the pinion seal and side seals, crush sleeve, carrier and pinion shims, pinion nut, ring gear bolts, marking compound with a brush, and RTV for the cover.

The IRS carrier comes out of the car as a unit, so once it is on the bench it makes sense to replace every bearing and seal rather than chase one noise and pull it again later. This is the kit to use with a gear ratio change or a limited-slip swap, and for a rear that has started to whine or leak at the pinion or side seals.

Setup order for the GM 8.6 IRS: drive the new pinion races in, set pinion depth with shims, crush the new sleeve to spec while checking rotating torque with an inch-pound torque wrench, press the carrier bearings on, then set backlash and read the pattern with the marking compound before the cover goes back on.