Travis, get the car up in the air and eyeball everything, driveshaft, halfshafts, center support bearing. Then go hands on. Give all of those rotating parts a good shake, move them around, twist them. If anything is bad enough to make that much noise, it's a fair bet you'll locate it. It kinda sounds like when you put it in reverse or apply the brake, you are taking the load off of a worn out component and it's telling you that it's worn out by being noisy. I hope you'll be able to find it or at least narrow it down. Good luck..
1987 BMW 325
[This message has been edited by jeffsr (edited 04-19-2000).]