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Shop now for Parts and Tools for 2020-Current GM 3500 series trucks with AAM 12" Rear Axles.
GM used American Axle Manufacturing (AAM) 12" rear axles in 2020-2023 Chevy Silverado and GMC Sierra 3500 Dual Rear Wheel Pickups and Chassis Cab models. The AAM 12" rear axle is a conventional, integral type housing hypoid gear iron-beam axle with two pinion bearings. The AAM 12" Rear Axle was first used by Ram in 2019 Ram 3500 trucks. For General Motors, the 12" dually axle was new for the 2020 model year replacing the 2003-2019 AAM 11.5" axle.
There are a couple of surprising old school design elements for these axles. One is the clutch type limited slip differential that uses a flyweight type differential governor assembly instead of the more modern mechanical gear type or electric locking differentials. The other VERY old school design is the pinion nut gets staked to the pinion shaft threads in two places.
A reusable, right-hand thread single spindle nut is used for rear wheel bearing adjustment and retention. The nut is locked in place on the spindle by a square steel key. A non-reusable snap-on retainer prevents the key from slipping out of place.
A single-use gasket is used to seal between the 43mm x 33 spline full-float type axle shaft and wheel hub. The axle shaft is retained by QU30121 1/2" bolts with factory applied threadlocker. Eight bolts are used.
An unusual feature of these axles is the axle shafts have extra long splines for the Speed Reluctor Rings (aka ABS Tone Rings) which are attached to the outboard side of the differential bearing adjuster nuts.
The wheel bearings must be packed with grease to provide initial lubrication. In service, 75w90 Synthetic Differential Oil that travels into the wheel hub from the differential will provide long-term wheel bearing lubrication.
The brake rotor is a separate part that bolts to the back side of the hub with 8 bolts.
