Yukon Gear Positraction internals For 8.5in GM w/ 30 Spline Axles
The 30-spline GM 8.5 ten-bolt is a favorite for Chevy and GMC trucks, Blazers and built street cars, and a lot of them now run a Yukon Dura Grip posi. When that unit starts clunking or the cover comes off to reveal a chipped pinion gear, the Yukon Gear & Axle YPKGM8.5-P-30 lets you rebuild the gear side of the Dura Grip instead of replacing the whole carrier. It is a spider gear set for a GM 8.5 already fitted with a Dura Grip and 30-spline axles. Clutches are not included.
The ring gear drives the Dura Grip case, and a cross pin through the case carries two pinion gears. Those pinions mesh with two side gears splined to the 30-spline axle shafts. Behind each side gear is a composite clutch pack. When you get on the throttle, the pinion gears try to push the side gears apart, which squeezes the clutch packs and ties the two axles together so the tire with grip keeps pulling. In a turn, the gears let the outside wheel overrun while the clutches slip. Thirty-spline 8.5s often live behind big engines or bigger tires, so the cross pin and pinion gears take a lot of shock load. Because the 8.5 uses C-clip axles, the cross pin also keeps the C-clips from walking inward. This set includes two side gears, two pinion gears, the cross pin shaft, the roll pin and the spider gear thrust washers.
Chatter in tight turns is usually oil or clutches, not gears; see our friction modifier guide first. For the common 8.5 failure points and what a full rebuild costs, read GM 8.5 10-bolt problems and rebuild cost.
Three things have to match. The axle must be a GM 8.5 ten-bolt; the cross pin lock bolt on an 8.5 takes a 5/16 in. wrench, which sets it apart from the older 8.2. The axle shafts must be 30 spline; pull one and count, because 28-spline 8.5s are just as common in older cars. And the carrier must be a Yukon Dura Grip. This set is not for an open case, a factory GM posi or another brand of limited slip. Our 8.5 and 8.6 identification guide shows how to separate the housings.
Fits the GM 8.5 in. ten-bolt with 30-spline axles that is already running a Yukon Dura Grip 30-spline 8.5/8.6 posi. Since the set fits the carrier, the vehicle year is less important than what is in the case. Yukon lists this set for the 8.5; if your Dura Grip lives in an 8.6, send us the year and VIN with a photo of the carrier and we will confirm it before shipping. If you have a 28-spline 8.5, it needs the 28-spline version instead. Browse more axle parts on our hard parts page.
The carrier can stay in the housing. Drain the oil, pull the cover, drive out the roll pin and remove the cross pin. Push the axles in, take out the C-clips and slide the axles out a few inches. The Dura Grip side gears are under spring preload, so rotate the gears out through the case window; a posi gear rotating tool helps. While the clutch packs are exposed, check them for wear and glazing and replace them if needed. Lube the new parts with gear oil, rotate them in, then refit the C-clips, cross pin and roll pin. The ring gear stays put, so backlash should not change; Yukon lists 0.006 to 0.011 in. for the 8.5 and 8.6. Refill with non-synthetic GL-5 gear oil and limited slip additive.
If the carrier bearings are noisy, the Yukon carrier installation kit with HD bearings fits the larger bearing journals used on aftermarket 8.5 carriers, and the Yukon master overhaul kit for 8.5 axles with an aftermarket posi adds pinion bearings, seals and shims for a full refresh.
| Brand | Yukon Gear & Axle |
| Part number | YPKGM8.5-P-30 |
| Fits | Yukon Gear Positraction internals For 8.5in GM w/ 30 Spline Axles |
| Type | Ring & Pinions |
| 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.
No. It is the gear set only: two side gears, two pinion gears, the cross pin shaft, the roll pin and the spider gear thrust washers. Clutch packs are separate.
No. Yukon lists this set for a GM 8.5 fitted with its Dura Grip positraction. Factory GM posi units use their own internals.
Pull an axle and count the splines on the inner end. Many cars use 28-spline shafts and many trucks use 30, but swaps are common, so count rather than guess.
No, as long as the ring gear and carrier bearings are left in place. Check backlash with a dial indicator before closing the cover; Yukon lists 0.006 to 0.011 in.
Yukon recommends a non-synthetic GL-5 gear oil with its limited slip additive for the Dura Grip. Synthetic oil can cause aggressive or noisy clutch engagement.
