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  1. #1

    Question Thump at random when stopping (2012 Silverado 2500 HD 4x4 Duramax Allison)

    I am experiencing a thump at random when stopping my 2012 Silverado 2500 HD 4x4 Duramax Allison. The truck has done this since within a week of purchasing it new. At first I thought it was just me, then I thought maybe it is the fuel or DEF tank sloshing from maybe not enough baffles. Now 9 months onto having the truck I am sure it is something else. It happens pretty random and I can go 1,000 miles without noticing it. When I do notice it, it can feel like anything from a simple pop to like a soft rear ending. I have read elsewhere of people experiencing the same with older vehicles but I have not really found much on post 2010 trucks and REALLY not much on the Duramax/Allison configuration. It almost feels like something is not disengaging or engaging at the right time but it doesn't happen all the time. In those issues I have read about there has been talk about greasing things on the shaft and that only works temporarily and only a FEW people have gotten their dealer to have items replaced. Hoping someone from GM might drift by on here and weigh I on this. I would prefer to go to the dealer informed when I go... (that definietely healped when I had a buzzing sound and I knew what it was and how to fix it as they did not. (kinda like on one of my Dodge Rams when I asked them to lube my 4wd U joint and they just sprayed lube on it and didn't know there was a needle hole fitting that actually needed grease)
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  2. #2


    The propellor or tailshaft (same thing) has been known to make a thump/bump/ or clunk even on the newer trucks, GM's fix is to first pack the tailshaft splines with grease, if this doesnt solve the problem then they may install a new nickle plated yoke.
    For some reason this glitch hasnt been totally resolved on the 07-13 model trucks, maybe the next gen trucks have the problem resolved.
    Other items to look at are the spare tire for security up against the bottom of the bed, the spring shackles for tightness and security, and the axle "U" bolts for proper torque and security.

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