I'm getting a thump on take off in my 2000 Z28 w/5.7L. It only happens when I start from a dead stop. The harder the takeoff, the more that you can feel/hear a thump. It doesn't happen any other time. I thought maybe it was a broken tranny mount, but it seems to possibly comming more from the rear, but I can't really tell. Can somebody give me their thoughts on what this might be?

 

Have you checked the tranny mount yet or just ruling it out beause it sounds like its coming from the rear?

 

A loose LCA bolt will do this too.

 

This is more than likely the damned stock tranny mount, happened to me in my 96 Z/28 and my boy with his 95 TA, jack the front of the car up and take a peek

 

Ive heard of the tips/muffler hitting underside heat shield, LCA bolt, or tranny mount....

 

I haven't had a chance to lift the car and check it. My schedule doesn't allow for much free time, so I am hoping to get some ideas what it would be best to check first. One additional piece of info, that might be helpful, is that this started right after I was accelerating hard across a train track crossing and had severe rear wheel hop.
Thanks for the responses so far.

 

sounds like the tranny mount

 

As someone who replaced 2 while I had my Camaro, I would guess the tranny mount too. Man did it scare the crap out of me the first time though!

 

i would say tranny mount too, i had the same thing

 

I had the same problem, also thought it was a transmission mount. It wasn't. Turned out the nut on the bolt holding the panhard bar on the passenger side had jumped a few threads and was loose. I ended up having to cut the bolt off. Once I replaced it, the thump was gone.

 

Tranny mount
Motor mount
LCA bolts
Track arm mount or bolt
U-joint

 

Finally got a chance to look at this problem. I can confirm that it's not the panhard bar or LCA bolts. Taking a break ... Next step is to move my jack stands and check the tranny mount.

 

For those of you whose said tranny mount ... take a bow.

The rubber tranny mount was torn almost completely in half. I picked up an ES poly mount and now there's no more thump on takeoff. There is a marginal increase in vibration, but it is not severe. With the top down and the wind in my hair, I hardly cared. Besides, if I wanted a silky smooth ride, I'd have bought a Buick or a Caddy instead of a Z28.