The truck is a 2011 Silverado with four wheel drive. Ok so some times when letting off the gas mostly 2nd or 3rd gear there is a pretty good single thud/clunk noise seems to be more towards middle or front of truck. Has on occasion done it while downshifting from 3rd to 2nd and some times into 1st. If I let off the gas slowly doesn't seem to do it. Had all fluids checked not that long ago all were good levels trans fluid is still pretty red no leaks.

 

Is this when in 4 wheel drive?

 

In two wheel drive and only some times if i try i can some times get it to do it a little more often.

 

So have an update got a transmission fluid change because was do anyways and had the noise checked by my mechanic and a dealer to see if it would be covered under my extended warranty. Dealer says its gear lash but i don't trust them any further then i could throw one of them but my mechanic checked everything underneath during fluid change couldn't find anything as far as u joints or bushings or alike. So could it be something maybe but will keep an ear out because its only when letting off the gas in lower gears and only some times unless im trying to make it do it. And it might be tolerance stacking that's now starting to show. Will probably do a transfer case fluid change soon as well.