Loaded open carrier for GM 8.5 and 8.625 10-bolt axles with 30-spline shafts and 2.73 and higher ratios. Swap in a new case when the old one is worn out.
A clunk every time you get on and off the throttle, a bang in tight parking lot turns, or chunks of spider gear on the cover magnet of a Silverado, Sierra, Tahoe or older Chevy car with the GM 10-bolt axle usually means the differential case and its gears are done. GM8.6L is a complete loaded open carrier for the GM 8.5 inch and 8.625 inch 10-bolt with 30-spline axle shafts. It arrives with the side gears, spider gears, cross shaft and thrust washers already installed, so you replace the whole wear assembly at once instead of rebuilding a tired case.
The ring gear bolts to the flange of this case, and the case spins on two carrier bearings in the housing. Inside it, two spider gears on the cross shaft walk around the two side gears that are splined to the axle shafts, so the outside wheel can turn faster than the inside one in a corner. Thrust washers back every gear. Over time the washers wear thin, the spider gears hammer the cross shaft, and the shaft bore in the case wallows out. That slack is the clunk you feel. An open carrier sends torque to the wheel with the least grip, so if you want traction instead, look at the Eaton Posi for the 8.5 instead.
Pull the cover and drain the oil. Hold one axle shaft and rotate the other; excessive free play before the gears take up, or a rough feel, points to worn washers and gears. Check the cross shaft bore and the pocket faces behind the spider gears for wear steps. Carrier bearing growl that changes with road speed is a bearing problem and may not need a new case. If the ring and pinion teeth are pitted or chipped, plan on gears at the same time. You can also browse other differential hard parts.
GM8.6L fits GM 8.5 inch and 8.625 inch 10-bolt axles, front or rear, with 30-spline 1.31 inch axle shafts, and is the 2.73-and-higher ratio case. It will not take a lower numerical ratio ring gear, so read the ratio on your axle tag or count teeth before you order. Carrier bearings are not included, and the axle year decides which ones you need. Eaton notes that pre-1999 axles usually have the small bearing bore (2.89 in race OD) using LM102949 bearings and LM102911 races, while 1999-and-later axles usually have the large bore (3.06 in race OD) using LM603049 and LM603012. Measure your old race if in doubt, or send us the year and VIN. If you only need a bare case to reuse your own gears, see the Yukon 8.5 open carrier case.
| Part number | GM8.6L |
| Axle | GM 8.5 in and 8.625 in 10-bolt |
| Type | Open, loaded (internal gears installed) |
| Axle spline / diameter | 30 spline, 1.31 in shafts |
| Ratio range | 2.73 and higher |
| Carrier bearings required (not included) | 1999 and later: LM603049 / LM603012; 1998 and earlier: LM102949 / LM102911 |
| Position | Front or rear |
| Item weight | 16.35 lb |
No. Bearings are a separate purchase. 1999 and later axles usually take LM603049 bearings with LM603012 races; 1998 and earlier usually take LM102949 with LM102911. Measure the old race OD to be sure: about 3.06 in is the large bore and 2.89 in is the small bore.
It is the 2.73-and-higher case, so it works with 2.73 and numerically higher ratios such as 3.42 or 4.10. A lower numerical ratio gear set needs the other carrier break.
No. It is built for 30-spline, 1.31 inch axle shafts only. Count the splines on your shaft before ordering.
Yes, if the teeth are in good shape. Use new ring gear bolts with thread locker, then check backlash and contact pattern because a new case can change the setup.
No. It is an open differential. If you want both wheels to drive, an Eaton Posi or a locker for the 8.5 and 8.6 is the upgrade path.
Use 75W-90 gear oil or the grade shown on your axle tag or owner's manual. Friction modifier is only for limited-slip units.
