USA Standard Master Overhaul Kit For 2010 & Down GM & Chrysler 11.5in aam Diff

A 2001-2010 Silverado or Sierra 2500HD, a 3500, or a 2003-2010 Ram 2500 or 3500 has usually towed a lot by the time its rear axle starts to whine. The American Axle 11.5 in. ring and pinion in those trucks is stout, but its four tapered bearings wear, and once they do the noise only gets worse. The USA Standard Gear ZK GM11.5 master overhaul kit is the budget-minded parts set for rebuilding that early-design 11.5: new carrier and pinion bearings with races, a pinion seal, a full shim kit and the small parts to set the gears up again. USA Standard Gear is a Yukon Gear & Axle line, and this kit is new.

What the ZK GM11.5 does in the early AAM 11.5

In the 11.5 the axle shafts float in the hubs, so the center section carries torque rather than the weight of the truck. That torque passes through the pinion, which runs on an inner and an outer tapered bearing held at preload by a crush sleeve and nut, and through the carrier, which sits on two side bearings positioned by shims. When a bearing pits or the preload relaxes, the pinion moves, the contact pattern shifts toward the tooth edges and the gears get loud. The ZK GM11.5 replaces all four bearings and races together so the gears can be returned to their original setting. The published contents are carrier bearings and races, pinion bearings and races, a pinion seal, a complete shim kit, a pinion nut, a crush sleeve, thread locker, and marking compound with a brush and silicone. The bearings are Koyo. There are no ring gear bolts or cover gasket in the list, so reuse good bolts or buy them separately.

Symptoms this kit addresses

• A highway whine that changes when you lift off the throttle.
• Growl or rumble that gets louder with weight on the hitch.
• Wet pinion seal and oil spatter under the bed.
• A clunk on take-off or when shifting between Drive and Reverse, with play at the yoke.
• Bearing glitter or gray paste in drained gear oil.

How to confirm before you buy

Lift the rear wheels, put the transmission in neutral, and drop the driveshaft at the pinion yoke. Turn the pinion slowly by hand and feel for roughness, then push and pull on the yoke for end play. Pull the cover and paint a few ring gear teeth with marking compound. A clean but worn pattern on good teeth means an overhaul is the fix. Pitting or broken teeth mean new gears too, such as the GM 11.5 4.10 ring and pinion. Do not overlook the hub bearings: a dry full-floating hub can sound like a pinion bearing, and the GM 11.5 axle bearing and seal kit covers that end of the axle.

Fitment

This kit fits 2010-and-earlier GM and Chrysler 11.5 in. AAM rear axles: the 2001-2010 Silverado and Sierra 2500HD, 2001-2004 2500, 2001-2006 3500, 2007-2010 3500HD, the 2007 Classic models, and the 2003-2010 Ram 2500 and 3500. Around mid-2011 the 11.5 changed to a larger rear pinion race, 4.375 in. instead of the 4.125 in. design this kit uses, so a 2011 truck needs to be checked. Measure the outer diameter of the inner pinion race or send us your year and VIN. If you prefer Timken bearings, the Yukon YK GM11.5 covers the same axles. Other axle kits are in our rebuild kits category.

Install notes

• Record the old pinion depth shim and the ring gear pattern before you take anything apart; it is your starting point.
• Press the races fully home and check that no daylight shows between race and housing.
• Set pinion preload with the new crush sleeve, using the rotating torque spec for new bearings. Never loosen the nut to correct overshoot; install a new sleeve.
• Set backlash and carrier preload with the side shims, then verify the pattern.
• Seal the cover with the included silicone and refill with gear oil to the specification on the axle tag or in the owner's manual, plus limited slip additive where required.

What is the difference between the ZK GM11.5 and the Yukon YK GM11.5?

Both are master overhaul kits for the same 2010-and-earlier 11.5 axles. The USA Standard ZK GM11.5 uses Koyo bearings; the Yukon YK GM11.5 uses Timken bearings.

Will it fit my 2011 or newer Silverado or Ram?

Probably not. Around mid-2011 the 11.5 went to a 4.375 in. rear pinion race, and this kit is the 4.125 in. design. Measure the race or send us your VIN.

Are ring gear bolts included?

No. The published contents do not list ring gear bolts or a cover gasket. The kit includes silicone for the cover.

Does it include a crush sleeve and pinion nut?

Yes. The kit includes a crush sleeve, a pinion nut, a pinion seal and a complete shim kit along with the bearings and races.

Can I keep my original gears?

Yes, if the teeth are not pitted or chipped. Mark the existing contact pattern first and set the gears back up to match it.

What fluid goes back in?

Use the gear oil grade on your axle tag or in the owner's manual. Add friction modifier if the axle has a limited slip.