Picked up a another Camaro the other day and have some whine/humm noise from the rear. It only does it when im going over 20mph and accelerating. When i let off the gas the noise will stop.
Also when i let off the gas then back it will stumble, not sure if thats the right way to say that. It will almost die sometimes when im going slow and let off the gas for awhile. The car is an 85 Z28 with 305/auto. Everything else seems to be ok though, runs real smooth except for the above stuff

 

have you checked the differential and tranny fluid levels? Check the obvious first

Oh and welcome to the boards

 

Diff fluid was ok, is it possible that the fuel pump is that loud?

 

If it is an electrical pump it could be. Crawl under the back of the car and find someone you trust to turn the key but not start the car, see if you can duplicate the sound. Chances are if it happens only when the car is moving it could be a tranny or differential problem. Good luck