Ever since I got my 91' 318IS I had a whine that sounds like it's coming from either the transmission or rear end. This is my first E30 so I have no idea if it's normal or not and nothing to compare it to except for my Volvo which makes zero noises.

It is most pronounced at low speed acceleration when going through gears. The noise sounds like the one you would hear when reversing. Is this normal? The transmission shifts fine otherwise. Should I only be hearing the engine?

I also noticed a slight whine when coasting on the highway which probably comes from the rear end. Once again, should I be hearing any noises or should it be completely quiet?

Both rear wheel bearings and axles are new. I also did fluid change in both diff and trans.