Im getting this thud when accelerating after coasting while driving. its not happening so much when shifting but really while i am already in gear. i previously changed the serpentine belt and as some of you know, the top motor mount has to come out in order to reach in there. after it was all back together the thud started to happen. me thinking it was something i did to the stock motor mount i then installed an aftermarket one for this problem to continue to happen. Any help would be greatly appreciated all the knowledge around me that i have asked does not know what the issue is.

 

Did you get a mount for a standard? Could be one of the other mounts got stressed. Could be axles.

 

Check all the other mounts. Since you would have had to jack up the engine to remove the front mount, you may have damaged one of the other mounts.

Posting the year and mileage would help. Gives those reading and answering a perspective of the condition of the car.

 

Sorry I just joined yesterday, fairly new its a 2008 with 135k. i replaced the two other mounts along with it. are you saying that my axles may be loose?

 

One of the descriptions of bad CV joints is a clunk if you let off the accelerator.
Other things include worn out LCA bushings.

 

A 2008 , ? Which engine? Ok I looked in your profile
a 2008 SS 2.0 did you replace the upper mount ? You say aftermarket, was it from Turbo Tech Racing or Anchor?
did you replace the front and rear transmission mounts?

 

The thud i am getting is when accelerating not when letting off.

 

I replaced all mounts the one i replaced first is an aftermarket yes.

 

But which brand can be the key, look thru the slot in the passenger side front wheel well, if the bolt head is low in that oblong hole the upper mount is no good.
and the tensioner comes out the front , you don’t need to remove the upper mount. Like in this

https://www.chevyhhr.net/forums/ss-s...2-0l-ss-52577/

 

It is a turbo tech mount, i went to look in the slot but i could not find nor feel the head of the bolt.