Getting a small clunk while in reverse

[BraveUlysses]

91 318iS
135k

18 month old GC school Kit, including RSMs.

I'm getting a small occasional clunk at the rear (no specific side) when engaging reverse for the first time (does not repeat if I pull forward and try again).

Any thoughts? Diff bushing? CSB? Guibo? Subframe bushings? All are stock/original as far as I know.

I'm not getting any unusual vibrations or rattling otherwise.

Thanks

[jlevie]

Any of differential bushing, subframe bushings, trailing arm bushings, CSB, Guibo, drive shaft, transmission mount, or motor mounts. Get the car up in the air and inspect everything.

[BraveUlysses]

Just realized I summed it up wrong, it only happens when I apply the brakes for the first time while reversing.

[bloodshot-e30]

rear subframe is prob broken where the diff mounts... (ive had 2 E30s with it and this one has it as well so 3) lol

[BrettsE30]

brake calipers loose? or if all suggested above are fine it could be your trans or diff.

[72ratcamaro]

Mine does the same thing. I just chalk it up to the rear brakes settling down.

Probably somethign serious. But can't be bothered with it.

[mr ilia]

I get occasional "brake" noice while in reverse. I tacked it down to e-brake components hidden in the brake rotor.

[BraveUlysses]

I'll be sure to check that, thanks for the suggestion.

[Hellabad]

Without even pulling the wheels off, you can peek at the spring clips that put tension on the pads in the rear calipers.

There should be no metal "fingers" sticking up above the caliper. All of the metal should be under the edges of the hole in the middle of the caliper.