Insane noise

[Jordan325iC]

I had this noise pop up during an autocross. After the autocross, I jacked up the car to figure out what was making the noise, couldn't find it, put it back on the ground and it stopped making the noise. It was quiet for a few weeks, then it came back with a vengance yesterday.

Car: '88 325is, 250k miles, lowered w/ LSD.

The noise:
-Metal on metal clank. Very loud, basically undrivable.
-Occurs a few times each wheel rotation.
-Independent of gear or RPM.
-Is louder during braking.
-Goes away sometimes during left turns?
-Not completely constant, occasionally disappears briefly.
-From the rear of the car.

At first it was only when I was braking, then it was when I was taking certain turns, then it was all the time, then it disappeared, now it came back and is constant.

Anybody have any guesses as to what's going on?

[MikeE30325i]

could it be your lsd?

[Jordan325iC]

It's possible. But the fact that it gets worse during braking, goes away sometimes, and will disappear when the car is on certain left turns, makes me think not (or hopefully not :D ).

[PeaveyBassist]

Check the whole brake system in back. Calipers, pads, and ebrake shoes. Check the wheel bearings in back as well. Those dont usually make a metal/metal sound but its worth checking. Could also be subframe bushings. Just start shakin stuff in back and see if anything metal is touching metal, bushings that can move around a lot, etc.

Will