I have this clunk coming from the back of my car. My transmission shifts pretty damn hard, and I don't know if the clunk is from driveline shock, or if something is bouncing. It sounds almost like my gas tank is banging against the car or something, but I don't think that's possible.

I occasionally get a small clunk on the 2-3 at light throttle, but barely noticeable. The 1-2 clunk is very loud and apparent...if you guys want, I can get a video.

The rear U-joint on the LS1 driveshaft I installed also seemed to not be as loose as it should. Would a U-joint make a loud bouncing/clunking noise?

 

Mine does it but it is still the stock exhaust banging around on the old hangers, does you exhaust dump before the rear or go all the way out the back? You may want to see if that's it, also is there any way it's the torque arm? I am getting a clunk from under the car that I think is either the torque arm mount or tranny mount. But it is obvious it is under the car and doesn't sound like it is coming from the rear.

 

Mine dumps before the rear. It did this with my old exhaust too, and that exhaust had some TIGHT *** hangers. Torque arm mount is polyurethane, so I don't think that would be a possible candidate. My tranny mount is a fairly new LS1 mount.

I dunno I guess I'll just live with it if it's common. My friend Javier said his has done the same thing for the past 6 years. Problem is, it seems like it's gotten louder/more apparent over time. Oh well...