I've found a few posts about mixing weights of oil and I think I may try it. It gets cold here in New Hampshire but also pretty hot in the summer months so I'm ordering 2 quarts of MT90 and one of MTL. I guess this mix is pretty popular on some of the bimmer forums as well. My plan is to get the tranny happy first, then I'll tackle the rear end Thanks again guys.

 

When I did mine, I found that the transmission oil was in much better shape than the rear diff. The 1-2 shift was a little stiff, but the oil was at least the right color and viscosity.

The rear differential was a completely different story. It came out like maple syrup and smelled terrible.

 

Personally i would do them both at the same time. That way they have the same change interval and everything is fresh and new. Kind of like doing front and rear brakes at the same time

 

Good point....Besides, getting covered in gear oil two different days would suck. I'd rather smell that crap once. I actually had a bottle of 70-90 dump in an apartment closet once..never got the stenchl out.

 

i have no idea why the tranny and diff oil always smells like cows *** but tis def not a good thing to spill. plus having to jack the car up twice and do work is never fun, be one and done.

 

MT-90 for sure, made my O2J happy now using it for my 6 spd, don't forget to drain the bevel box in a quattro car

 

I'm assuming that you're referring to the rear differential? As far as I know the quattro manual transmissions share oil for the front and center differentials. The automatic has separate oil for the center diff.

 

Today i changed my diff seal and my diff oil and man that oil smelled worse than crap.

 

It's pretty nasty stuff.

 

no, the bevel box, just behind the tranny on my 01 TT 225Q transfers power to the rear diff, theres a post on it somewhere showing its location, its not even mentioned in my factory manual!!!