It Drives But Wont Reverse!!!

[crawlin duckies]

ok so i put a motor from a helicopter in my car and i took the batteries and the crystal and the antenna and i never smelled anything funny... i drove my car around and i was drifting on the hardwood and i hit the wall with the side of my car.... i started to move but i hit the door frame not to hard (like an inch from where i hit the wall) and i tried to back up, all it did was make a buzzing or whirring sound and i checked to see if the gear cover was on right and if the heat sink for the motor was on to thight and it was so i loosened it half a turn and it still buzzes...... can any one tell me what might be wrong??? thanks