Rear Axle Clunk Sound

Some 2015-2021 Colorado and Canyon models may have a clunking sound heard from the rear axle area when driving over railroad tracks and/or entering or exiting parking lots and driveways. The sound may be caused by excessive axle shaft end play.

To determine the source of the clunk sound, first apply the brake pedal while another technician lightly shakes the vehicle with a lateral force to the bed of the truck near the tail lamp area. If the sound persists while the brake is applied, inspect the leaf spring shackle for excessive movement or debris within the leaf pad springs. Refer to Bulletin #17-NA-394 for more information.

If the sound only occurs when the brake pedal is not applied, check for excessive end play within the rear axle. (Fig. 11) The C-locks on the axle shaft may require replacement.


Fig. 11


Check End Play

Use a dial indicator to measure and record end play on each side of the rear axle by pushing and pulling on the brake rotor and axle shaft. (Fig. 12) If end play measurement is at 0.32 mm (0.0126 in.) or greater, the service C-locks can be installed without interference (review Bulletin #20-NA-156 for an exception on the G80 locking rear axle). If end play is less than 0.32 mm (0.0126 in.), the service C-locks may be installed; however, if the axle shaft and differential are at the low end of the tolerance, interference may occur.


Fig. 12


To access and install new C-locks if needed, remove the rear brake rotors and rear axle housing cover. (Fig. 13, #1) Use care not to damage the axle seal when pushing the axle shaft inwards. Be sure to tighten the pin lock bolt to specification.


Fig. 13


C-Lock Specifications

The production C-locks have a thickness specification of 5.18 mm to 5.26 mm (0.204 in. to 0.207 in.) while the service C-locks have a thickness specification between 5.42 mm and 5.50 mm (0.213 in. to 0.216 in.

If end play exceeds 1.05 mm (0.0413 in.), the end play is out of specification. Refer to appropriate Service Information for further drive line diagnostic procedures.

For additional information and part numbers, refer to Bulletin #20-NA-156.


– Thanks to Matt Singer

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