Yukon Gear Mini Spool For GM 8.5in w/ 30 Spline Axles
Yukon YP MINSGM8.5-30 is a mini spool for the GM 8.5-inch 10-bolt rear axle with 30-spline axle shafts. It replaces the spider gears and side gears in a standard open carrier and locks both axle shafts together, so both rear tires turn at the same speed all the time. People who buy it usually run a GM 8.5 in a drag car, a dedicated off-road truck or a trail rig and want full lockup for much less money than a locker or a full spool.
In a stock open GM 8.5, the ring gear turns the carrier case. A cross pin in the case holds two spider gears, and they drive two 30-spline side gears on the axle shafts. The spider gears let the wheels turn at different speeds, which is also why an open differential sends power to the tire with the least grip. The mini spool removes that. It fits inside the existing open case where the spider and side gears were, takes both axle splines, and is held by the case cross pin. The case, ring gear and carrier bearings stay the same. With the two shafts connected, a spinning tire can no longer take all the power. Yukon says it delivers 100 percent of the power to both tires at all times.
The tradeoffs are real. With both wheels locked, the rear tires scrub in every turn. Expect chirping, faster tire wear, push in tight corners and more stress on the axle shafts. Yukon does not recommend mini spools for street-driven vehicles. It recommends a full spool for vehicles with large tires or high horsepower, because the open case is still the weak link. Our open vs limited slip vs locker guide compares the options. For a truck that is also driven on the street, the Yukon Dura Grip posi for GM 8.5 30-spline or the Grizzly locker is the better fit.
Confirm it is a GM 8.5 10-bolt. Check the cover shape, count the cover bolts and read the axle code. The GM 8.5 problems and rebuild guide and the 10-bolt vs 12-bolt guide explain how to identify it. Count the axle shaft splines, because 8.5 axles came in 28 and 30 spline, and this part is for 30 only. Check that the carrier is a standard open case. A factory G80 locker or a posi carrier has a different interior and will not take a mini spool. If the case is cracked or the cross-pin bore is worn, start with a new Yukon GM 8.5 open case.
Yukon lists YP MINSGM8.5-30 for GM 8.5-inch rear axles with 30-spline axles, installed in a standard open carrier case. The listing does not give a year range. The GM 8.5 was used in Chevrolet and GMC half-ton trucks and SUVs as well as older passenger cars, and spline count changed over the years. Count your splines and confirm the carrier type, or send us your year and VIN before ordering.
| Brand | Yukon Gear & Axle |
| Part number | YP MINSGM8.5-30 |
| Fits | Yukon Gear Mini Spool For GM 8.5in w/ 30 Spline Axles |
| Type | Differentials |
| Condition | New |
| Ships | Same business day (in stock), from the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
Yukon does not recommend mini spools for street-driven vehicles. Both rear wheels are locked all the time, so tires scrub and chirp in turns and wear faster.
No. This part number is for 30-spline axles. Count the splines on your axle shafts before ordering.
No, if your standard open case is in good condition. The mini spool installs in the existing open case in place of the spider and side gears. A worn or cracked case should be replaced first.
No. It is made for a standard open carrier case only.
Yukon recommends a full spool for vehicles with large tires or high horsepower, because the open case is still in the load path with a mini spool.
75W-90 gear oil. There are no clutches in a spool, so no friction modifier is needed.
