Is Redline MT90/MTL safe for late model Audi's?

[Tusin]

So based on the recommendation that I recived here, and also on some of the Audi based forums. I replaced my gear oil with a mix of MTL/MT90. Mainly to smooth out cold weather shifting (live in Alaska), and smooth out shifting in general.

My thread on the Audi forums has sparked a debate that no one can seem to answer correctly.

I am not a transmission guy, but how I understand the late model (B6/B7) transmission/diff setups to work. Is the gearbox/front diff and torsen (if quattro) all share the same fluid. Well our front diff is a hypoid setup. And according to Redline's website MT90 and MTL is not to be used in a hypoid diff.

So far everything is running pretty dang good with the MTL/MT90 mix. No odd noises or anything like that.

Any input?

(sorry for making a separate thread about this, just felt like it deserved it's own).

 

[m37charlie]

What does the owners' manual call for in the front diff?
Do they give a spec in the GL4 vs GL5 category?

Charlie

 

[cos]

This might help: I just had a look at the Amsoil guide for a '07 Audi A3 and they spec their MTG (the equivalent of Redline MT90) for the manual trans.

 

[kmoni]

Audi (and VW) would like you to put 90 weight oils in. That being said, I've been running straight MTL in my A4 for the past 100K miles. The MTL helps a lot with the 1-2 shift in winter. I contemplated adding some MT-90 during the last change, but didn't.

If I was tracking my car, I would change to 90 weight for the added protection.

 

[Tusin]

I understand that the viscosity is fine. Straight MTL, mix, straight MT90. But what we are trying to research (even some of the forum sponsors at audizine aren't 100% sure). Is if running MTL/MT90 is safe for the Audi hypoid front diff. I think the question is more of, is GL4 really safe for the hypoid front diff.

I would think it would have to be, as we need a fluid that is yellow metal safe for the gear box. But the gear box and diff share the same fluid.

 

[bmwtechguy]

Redline 75W-90NS is GL5 and has no friction modifiers for limited slip diff use. If I wanted or needed GL5, this is what I would use.

 

[kmoni]

Apparently Audi is not very good about specifically specifying GL4 or GL5 for the transmission. The consensus (on Audiworld at least) is GL4 for the trans/torsen and GL5 for the rear diff.

I've heard that the factory fill is Castrol.

 

[Tusin]

Yeah they are very bad at specifying what factory fill is. The PN number is G52 911 A2 (or A1 for the .5 litre size). It has a viscosity rating at 100c of I think 14.2, so it is close to a 75w90 I believe.

But yeah, a lot of A4 owners have been running GL-4 in their gearbox/diff, with no issues. Just was looking for some information from the experts on here