Motive Gear 3.73 ring and pinion plus master bearing kit for the GM 8.6 in (8.625) 10-bolt rear axle in 1999-2008 trucks and SUVs. Full regear in one box.
Most people shopping for this kit own a 1999-2008 Silverado 1500, Sierra 1500, Tahoe, Yukon or Suburban 1500 that either howls from the rear at highway speed or feels flat since it started towing or wearing taller tires. This bundle covers both jobs in one order: a Motive Gear 3.73 (41/11) standard-rotation ring and pinion for the GM 8.6 in. 10-bolt, plus a master install kit with every bearing and setup part the regear needs.
The 8.6 (8.625 in. ring gear) is the C-clip 10-bolt GM put under its half-ton trucks and SUVs once they moved to rear disc brakes. The pinion rides on two tapered bearings held under load by a crush sleeve, and the carrier spins on two side bearings with shims that set backlash. Going from a factory 3.08 or 3.42 to 3.73 multiplies torque at the wheels by roughly 9 to 21 percent, which is what lets a 4.8 or 5.3 pull a trailer or 33 in. tires without the transmission hunting for gears. In the box: the ring and pinion, tapered pinion and carrier bearings with races, pinion seal, shims, crush sleeve, pinion nut, ring gear bolts and the cover gasket.
Read the RPO sticker in the glovebox: GU6 means 3.42 gears and GT4 means 3.73. Count the cover bolts (ten) and check for rear disc brakes, which separate the 8.6 from the drum-brake 8.5. Our 8.5 and 8.6 ring and pinion buyer's guide walks through telling these apart from the 7.5, 7.625 and 8.2 10-bolts, which take different gears, and the 10-bolt problems and rebuild cost guide explains how to tell gear noise from wheel bearing noise before you tear in.
The listing is for the GM 8.6 in. 10-bolt rear in 1999-2008 trucks and SUVs: Silverado 1500, Sierra 1500, Tahoe, Yukon, Suburban 1500 and Yukon XL 1500. The ring gear size is shared with the 8.5 in. 10-bolt, but older 8.5 axles may have a different spline count and carrier, so check those before using the gears in one. The bearing kit is matched to the 1999-2008 axle; GM changed the pinion bearings in 2009, which is why later trucks need the 2009-and-up 8.6 overhaul kit instead. If you are unsure, send us your year and VIN, or browse our rebuild kits for the other 10-bolt kits.
Pull the C-clips and axles, then the carrier. Set pinion depth first with the shim under the inner bearing, crush the new sleeve slowly to reach preload, then shim the carrier for backlash and read the contact pattern with marking compound on both sides of the teeth. Yukon's setup chart lists the GM 8.5 and 8.6 at 14-19 in-lb of new pinion bearing preload and 0.006-0.011 in. backlash. Never back the pinion nut off once the sleeve is crushed; if you overshoot, install a new sleeve. If you would rather skip the crush sleeve, a crush sleeve eliminator uses shims instead. Fill with 75W-90 gear oil, adding friction modifier only if the axle has a clutch-type posi, drive easy for the first 500 miles and change the oil after break-in. Reprogram the speedometer for the new ratio, and consider a nodular iron 8.6 cover if the truck sees rocks or trailer duty.
| Axle | GM 8.6 in (8.625 in) 10-bolt rear |
| Listed fitment | GM 1999-2008 trucks and SUVs with the 8.6 in 10-bolt |
| Ratio | 3.73 (41/11) |
| Gear set | Motive Gear, standard rotation |
| Install kit | Master kit: pinion and carrier bearings, races, seal, shims, crush sleeve, pinion nut, ring gear bolts, gasket |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
The gears are for the 8.6, but the included bearing kit is for 1999-2008 axles. GM changed the pinion bearings in 2009, so a 2009-and-up truck needs the later bearing kit.
Check the RPO sticker in the glovebox. GU6 is 3.42 and GT4 is 3.73. You can also count the ring and pinion teeth with the cover off and divide.
New gears run on the old bearings will lose their setup quickly and start whining. The pinion has to come out for a regear anyway, so replacing every bearing at once is the only way to get a quiet, lasting result.
Yes. Changing from 3.42 or 3.08 to 3.73 makes the speedometer read wrong, so reprogram the axle ratio with a tuner or have a shop update it.
75W-90 gear oil. Add friction modifier only for a clutch-type posi, and change the oil after the first 500 miles of break-in.
