Crazy Transmission Whine/Howl

[ArtFoodBMW]

87 325i, swapped to manual from 91 325i vert.

I thought the howling was coming from the differential, since it didn't come from my parts car. Swapped the diff with a known-working unit the other day and the whine continues.

It sounds like the whine is coming from the transmission.

It occurs at all speeds, but the sound varies in pitch. Occurs all the time both coasting and driving in and out of gear.

The sound goes away after the fluids are warmed up (15-20 minutes of driving)

I did not change the fluid when I installed the transmission because the fluid still had good color, and was full.

Any ideas?
Redline MTL? Fluid additive?

Thanks fellas

[Mook613]

Sounds like you have the wrong fluid in there.
If you have a hex head set then it's not too bad of a job to change the fluid.

Get some Redline MT or MTL-90 and know that you have the right stuff in there.
Also, use some clear silicone on the drain plug to ensure that it seals up (mine didn't and ended up having to do the job twice).

[Campbelljj]

Had same issue on my swap. Drained and refilled with Redline mtl. Whine disappeared after 1/4 mile. Good luck!