Automatic Transmission problems of the 2003 Nissan Sentra

I purchased my Sentra in Dec of 2002. One week after I bought it, I had to take it in because it clunked when you turned the wheel. Took it back to dealer and front suspension was loose. Fixed the clunk. Started to notice that 2 qts of engine oil was gone and the coolant level kept dropping even though I kept pouring more in. Took it back to dealer, claimed there was air bubble in engine and to let it go. Still noticing engine oil smell and coolant level low. Dealer claims nothing is wrong. Passenger side window leaks, had run channel replaced twice. Around 7000 mi, I noticed that the tranny squeaked b/w 3rd and 4th gear. Been to dealer 4 times, claim to tighten mount bolts, belts, and exhaust manifold. Still squeaking. Rear bumper is now falling off and gear shift is starting to stick. Had rear brakes adjusted at 7500 mi and again at 11000 mi. Brakes still seam spongy and lose stopping ability. Been to dealer around 20 times since December.

My car moves forward while in park. My rear bumper is beginning to fall off. Two loud and annoying grinding noises in the front driver and passenger side of the car. Brought it in to two Nissan dealerships and only one problem has been fixed since then.