Yukon Gear Master Overhaul Kit For GM 8.5in Diff w/ Aftermarket Positraction

Built a GM 8.5 in. ten-bolt with an aftermarket limited slip or locker and now it hums, leaks or needs a fresh setup? A standard GM 8.5 bearing kit will not fit most aftermarket carriers, because many of them use larger carrier bearing journals than the factory case. The Yukon Gear & Axle YK GM8.5-HD is the new master overhaul kit made for the GM 8.5 in. rear with aftermarket Positraction, with Timken bearings and races sized for those heavy-duty carriers.

What the HD master kit does in a GM 8.5 rear

The 8.5 in. ten-bolt is GM's corporate C-clip rear, used under muscle cars, G-bodies and half-ton trucks and a common home for a performance carrier. The pinion rides on two tapered bearings preloaded by a crush sleeve, and the carrier is held by two side bearings whose shims set backlash and preload. What makes this kit different is the carrier bearing size. Yukon's matching carrier kit for the same axle is listed for 8.5 in. differentials using a Yukon Dura Grip, Eaton Posi, ValueTrac, TrueTrac, Pro-Series Auburn, Detroit Locker or a standard carrier with large bearing journals, and works with heavy-duty bearings. The YK GM8.5-HD combines those HD carrier bearings and races with pinion bearings and races, a pinion seal, a complete shim kit, ring gear bolts, pinion nut, crush sleeve, thread locker, gear marking compound with a brush and the cover gasket.

Symptoms that point to the rear end

• A whine that rises with road speed, worse on either drive or coast
• Bearing growl that changes when you weave the car or truck under load
• Chatter or binding in turns from a clutch-type posi that is worn or running the wrong oil
• Pinion seal leaks onto the yoke and driveshaft
• A clunk on takeoff or when shifting into gear, from bearing play or a loose pinion

How to confirm it before buying

Pull the cover and identify your carrier first. Look for the maker's name or tag on the case and measure the carrier bearing journals or read the numbers on the old bearing cones. A factory open or GM posi carrier with standard journals takes the regular kit, such as our GM 8.5 rear master overhaul kit with Timken bearings; a large-journal aftermarket unit takes this HD kit. Then check the old oil for metal, inspect the gear teeth and rock the pinion yoke for play. Chipped or pitted teeth mean new gears; a GM 8.5 3.73 30-spline ring and pinion pairs well with this kit on a re-gear.

Fitment

Yukon lists this kit for the GM 8.5 in. rear differential with aftermarket Positraction. It is a rear-axle kit; the GM 8.5 front axle used in four-wheel-drive trucks has its own GM 8.5 front master overhaul kit. It is also not for the older BOP 8.2 or Chevrolet 8.2 ten-bolts. Because aftermarket carriers vary, confirm your carrier brand and bearing size before ordering, or send us the carrier make plus your vehicle's year and VIN and we will check fitment. See more axle kits in our rebuild kits collection.

Install notes

• Remove the C-clips to pull the axles: take out the cross pin bolt and cross pin, push each axle in, and lift the clip out. Some aftermarket carriers use a different cross pin or retention method, so follow the carrier maker's instructions.
• Expect to shim the carrier from scratch; an aftermarket case rarely matches the old shim stack. The kit's shim assortment is there for that.
• Set pinion preload in small steps against the new crush sleeve and check rotating torque each time.
• Use thread locker on the ring gear bolts and verify backlash and the contact pattern before buttoning up. A Yukon hardcore GM 8.5 cover adds protection for trucks that see rocks.
• Fill with 75W-90 gear oil. Clutch-type posi units generally need a limited-slip friction modifier; gear-type and locker units usually do not. Follow the carrier maker's oil instructions.

What is the difference between this kit and a standard GM 8.5 overhaul kit?

The carrier bearings. This HD kit is made for aftermarket Positraction and locker carriers that use larger carrier bearing journals. A factory carrier with standard journals takes the regular GM 8.5 kit.

Which aftermarket carriers need the HD bearings?

Yukon lists its matching GM 8.5 HD carrier kit for the Yukon Dura Grip, Eaton Posi, ValueTrac, TrueTrac, Pro-Series Auburn and Detroit Locker, plus standard carriers with large bearing journals. Always confirm by measuring or reading your bearing numbers.

Will it fit the 8.5 front axle on my 4x4 truck?

No. This is the rear-axle kit. The GM 8.5 front differential has a separate master overhaul kit.

Does the kit include axle bearings or axle seals?

No. It covers the carrier and pinion bearings and races, pinion seal, shims, ring gear bolts, pinion nut, crush sleeve, thread locker, marking compound and cover gasket.

What gear oil should I use?

75W-90 gear oil. Clutch-type posi units generally need a limited-slip additive; check the instructions that came with your carrier.