I've got a 95 LT1, with about 2k miles on a completely stock rebuilt LT1. 50k on the trans.

When I'm driving > 50 mph and I release the accelerator, I get a rumbling and rough engine brake. The entire car will shake pretty bad. I can put the car in nuetral and it decelerates smooth (ie: but no engine braking). I'm starting to think it's the trans going out. Any ideas?

Thanks,
J

 

maybe your exhaust system is loose.
When you decelerate it seems to vibrate the exhaust system much more.