Differential Unit problems of the 2011 GMC Sierra 1500

Differential makes cracking noise, lum bar on drivers seat doesn't inflate,.

There is play in the rear axles that emit a clunking noise when I am slowly backing over a grade with the steering wheels turned. I demonstrated play in the rear axles to the GMC factory rep and he said the axle play is within tolerances. My contention is that the noise is not normal and that the grooves in the differential end or the axles that accept the horseshoe shaped keeper clips are machined incorrectly and putting excessive stress on the clips. Eventually the clips will fail resulting in the wheel coming off. I further argue that if the axle play is indeed within tolerances then the tolerances are wrong. I tried to make the incorrect tolerance argument to the factory rep by making an analogy to the corvair and he missed my point. The rear suspension on the corvair was also within tolerances and many people died.

When I first drove my new truck I noticed a subtle knocking noise coming from the rear when driving slowly over a bump. The dealer’s mechanic agreed there was something wrong and called gm tech assistance (71-910-553230) and found the rear axle had too much play. The grove on the axle that retains the c retaining clip was machined too close to the end of the shaft. They replaced the axle. Only a person with mechanical experience could have detected the subtle noise. Had it gone undetected eventually the c clip would likely fail and the axle and wheel would have slid out of the differential housing. I doubt this machining fault on the axle is unique to my truck.