Yukon Gear Rear Differential Cover Kit for General Motors 8.6in Rear

A wet, oily rear cover on a Silverado, Sierra, Tahoe, Yukon or Suburban 1500, a cover that got caved in on a rock or a hitch, or a rear end that is already apart for gears or bearings are the usual reasons to replace the cover on a GM 8.6 inch 10-bolt. Yukon YP C5-GM8.5-KIT is a complete steel replacement cover kit for that axle: the cover, the gasket, the cover bolts and the fill plug come in one box, so you are not hunting for hardware with the truck on stands.

What the cover does on a GM 8.6 rear axle

The GM 8.6 is a Salisbury-style rear axle, which means the center section is part of the housing and the carrier is serviced from the back through the cover opening. The cover seals that opening, holds the gear oil the ring gear slings up to feed the pinion and carrier bearings, and on these axles it also carries the fill plug, so the fill height is set by the cover. A dented or flexed cover can let the gasket weep, change the oil level, and in a bad hit put the cover close enough to the ring gear to rub. On the 8.6 the cover is also the first thing you remove for every ring and pinion, carrier, posi or bearing job, and a used cover with bent flanges rarely seals as well the second time.

Symptoms that point to a cover replacement

• Gear oil seeping from the cover gasket line and coating the lower edge of the housing
• A cover that is dented, gouged or bent around the bolt flange from trail damage or a hitch strike
• A fill plug with stripped or damaged threads that will not seal or torque down
• Low gear oil found during service, followed by whine or bearing noise from the rear end
• The axle is already open for gears, bearings or a locker and the old cover and gasket are not worth reusing

If you are hearing noise along with the leak, our GM 8.5 and 8.6 10-bolt problems guide covers the common bearing and gear failures in these axles.

How to confirm before you buy

Clean the housing with brake cleaner, drive a few miles and look again. Oil that starts at the cover seam is the gasket or cover; oil that starts at the yoke is the pinion seal, and oil on the backing plates points at axle seals. Our cover leak guide explains when a new gasket is enough and when the cover itself is the problem. If the drained gear oil is full of glitter, plan on more than a cover: a GM 8.625 master bearing kit or new gears may be needed.

Fitment

The kit is listed for the GM 8.6 inch rear, described as fitting 2007-and-up GM applications, and the parts description calls it a steel cover kit for the GM 8.2 and 8.6 inch rears. The cover measures 9.75 inches wide, center to center between the side bolt holes. It does not fit the Trailblazer, Envoy, Rainier or Bravada, which use a 10.25 inch wide cover. GM built several rear axles in the same trucks, including the larger 9.5 and 9.76 inch axles, so count the cover bolts and measure across your cover before ordering. If you are unsure, send us your year, VIN and the RPO axle code from the glovebox sticker. Gear options for the same axle are in our GM 8.5/8.6 ring and pinion buyers guide and the rebuild kits section.

Install notes

• Loosen the fill plug first, so you know you can refill before you drain anything.
• Remove the old cover and scrape every trace of gasket or sealant off the housing face; any leftover material is a leak path.
• Wipe the face with solvent, fit the supplied gasket and run the bolts in by hand, then tighten them evenly in a crisscross pattern to the factory spec so the steel flange pulls down flat.
• The cover is listed as unpainted, so prime and paint it before installation if the truck sees salt or water crossings.
• Refill through the fill hole until gear oil reaches the bottom of the hole, using the grade in your owner's manual, and add friction modifier only if an aftermarket clutch-type posi is installed.
• Doing a full service? Inspect the spider gears while the cover is off; worn ones are covered by the Yukon 8.6 open spider gear set, and a regear can use the Revolution 4.10 ring and pinion for the 8.5/8.6.

What comes in YP C5-GM8.5-KIT?

The steel differential cover, a cover gasket, the cover bolts and the fill plug. A drain plug is not included, and the cover is not painted.

Will it fit my Trailblazer or Envoy?

No. The Trailblazer, Envoy, Rainier and Bravada use a wider 10.25 inch cover. This kit is the 9.75 inch wide cover, measured center to center across the side bolt holes.

How do I tell an 8.6 10-bolt from the larger 9.5 or 9.76 axle?

Count the cover bolts. The 8.5 and 8.6 use a 10-bolt cover, while the larger 9.5 and 9.76 inch axles use more bolts and a different cover shape. The RPO code on the glovebox sticker also identifies the axle, and we can check it from your VIN.

Do I need RTV with the supplied gasket?

Normally no. A clean, dry housing face and the new gasket seal on their own. Adding thick sealant under a gasket can let it squeeze out and leak. Our cover leak guide explains both methods.

How much gear oil does the axle need after the cover is installed?

Fill until the oil reaches the bottom edge of the fill hole with the truck level. Use the grade listed in your owner's manual, and add friction modifier only for a clutch-type limited slip.