Sometimes when I stop it feels like someone just hit me in the rear end.....I was told it was bad brakes but that did not fix the problem.....no one has been able to find it when they test drive the car since they only do a quick run down the road.....it happens sporadically......I can drive around town one day and it won't happen and then again I can be just gone on a quick run and when I slow down and just about come to a complete stop....BANG....sounds like and feels like someone just hit me in the rear end.....what can it be???????:banghead::banghead::banghead::screwy:

Check your motor mounts! Especially the one in tension when the transmission is in reverse. Open the hood and have one person look at the engine. Start it up, keep the parking brake set and one foot on the brake pedal, then put it in reverse and slowly increase the rpms and watch what the engine does. You might find your problem there.