Eaton Detroit Locker Differential 30 Spline 1.32in Axle Shaft Dia 2.73-5.13 Ratio Rear 8.5in/8.6in
If your Chevy or GMC 10-bolt leaves one rear tire spinning on a wet boat ramp, in snow or at the edge of a trail, an open differential is doing exactly what it was built to do: sending power to the wheel with the least grip. The Eaton Detroit Locker 187C148A replaces that open carrier in the GM 8.5 in. and 8.6 in. rear axle with a fully automatic locker for 30-spline axle shafts, so both rear wheels drive whenever the truck is going straight.
The Detroit Locker is a normally locked differential. In straight-line driving it ties both axle shafts together and sends torque to both wheels equally, even if one tire is in the air. When the truck turns, internal clutches let the outside wheel overrun and freewheel, then re-engage once you straighten out. There is no air line, switch or wiring, and Eaton calls the unit maintenance free. That is the trade-off to understand before buying: it is always working, so you will hear and feel it unlock and relock in tight turns, and on the street it changes how the truck behaves on and off the throttle in a corner. For a truck that tows, plows, launches hard or goes off road, most owners accept that for traction that never has to be switched on.
Check three things: the axle size, the shaft spline count and the ratio. The GM 8.5 and 8.6 are both 10-bolt-cover rears and look nearly identical, which is why this carrier is listed for both. This unit takes 30-spline axle shafts, so a 28-spline 8.5 will not work. Because the carrier break is 2.73 and up, it accepts every common ratio from 2.73 through 5.13, so you can keep your gears or re-gear at the same time. If your current gears are noisy or pitted, budget for a set like the Revolution GM 10-bolt 8.5/8.6 4.10 ring and pinion now, since the carrier has to come out either way.
Eaton part 187C148A is listed for the rear GM 8.5 in. and 8.6 in. 10-bolt with 30-spline axles, 1.32 in. shaft diameter, all ratios 2.73 and up. Those axles were used across decades of Chevrolet and GMC half-ton trucks, Tahoe, Suburban, Blazer and some performance cars, and GM changed bearing sizes, axle lengths and cover bolts along the way. Confirm the 10-bolt cover, the 30-spline count on your shafts and the ring gear size before ordering, or send us the year, model and VIN and we will check it. More lockers and limited slips for GM axles are on our hard parts page.
| Brand | Eaton |
| Part number | 187C148A |
| Fits | Eaton Detroit Locker Differential 30 Spline 1.32in Axle Shaft Dia 2.73-5.13 Ratio Rear 8.5in/8.6in |
| Type | Differentials |
| Condition | New |
| Ships | Same business day (in stock), from the USA |
| Warranty | 1-year |
No. It is built for 30-spline axle shafts. Count the splines on a shaft or check your build before ordering.
The carrier break is 2.73 and up, so it accepts ratios from 2.73 through 5.13 in the GM 8.5 and 8.6.
Many owners run them daily, but it is always locked when driving straight, so expect clicking in slow turns and a firmer feel in corners. If you want quiet street manners, a gear-type limited slip is the softer choice.
Eaton recommends a quality GL-5 petroleum gear oil, with synthetic allowed per the axle maker. Follow the gear oil grade the axle maker lists for your truck.
Yes. The carrier bearings have to come off the old case anyway, and new bearings with a fresh backlash and preload check are the right way to set up the locker.
