2000 Chevrolet Impala

After stopping heavy on my brakes and coming to a complete stop and then starting to take off, I get a " thunk" that occurs. I took my car to the brake shop and they tried to tell me it was a water bottle rolling around in my trunk(: )). So I took it to the Ford dealer and they did a total repair on the rear end axel and bearings($1700), which took care of a " scraping" noise that I was getting, but did not take care of that " thunk" when I begin to take off after stopping heavy on the brakes. I took the car back to the Ford dealer yet a couple more times and they were unable to find the source of the " thunk". Does anyone have any " good" ideas? It's definitely not the " water bottle" ( I took it out in order not to confuse any more repairmen).
January 21, 2006.

How many miles on the car? Check motor mounts, tranny mounts, and u-joints. Those are the most common causes of " clunks" OR, you could just QUIT STOMPING ON THE BRAKES ! It's very detructive to the brake system : lol:

Jan 22, 2006.