So is it GL-4 or GL-5 (Transmission oil question)

**youriy** · 04-21-2008 01:42 PM

Ok, so I just bought 3qts of Redline MT-90, was about to change it on the weekend but run short of the special tool needed to drain the tranny. Emailed a shop today and they said, just make sure it's GL-5 oil.
So I called Audi today and he went to look up the specs, and said it's GL-5 also.
So now I'm confused, Redline Mt-90 is GL4 which everybody reccomends here. I'm starting to think of bringing it back to exchange it for some Royal purple, which is GL5 I believe.

Thanks in advance for any clarification on this matter.

**youriy** · 04-22-2008 08:36 AM

ok, so, is it me, or nobody has ever changed their transmission oil?

**gtimart** · 04-22-2008 11:04 AM

Unless you have a very specific use for your car (track etc), I'd put whatever the dealer puts in it. Heck, I'd buy it from them or a reputable audi mechanic. I know an excellent place in Quebec City for Audi work. PM me if you want details.

**absolutegtr** · 04-22-2008 11:09 AM

The rear differential REQUIRES GL-5.

The transmission can take GL-4....I have had Redline MT-90 in my tranny for about 4K miles and love it.

**youriy** · 04-22-2008 05:13 PM

thanks for replies!

Audi fluid is 22$ per liter, Redline was 16$ and it seemed like it's the oil everybody uses here.

**diagnosticator** · 04-24-2008 03:54 PM

Originally Posted by youriy

ok, so, is it me, or nobody has ever changed their transmission oil?

OK, the MT shares the lubrication of the differential with the transmission gears, the differential is a hypoid gear, and would "like" GL5 lube, but GL5 is too slippery for the transmission synchronizers, so Synthetic GL4 is the required specification.

**Splattj** · 04-24-2008 04:32 PM

Originally Posted by diagnosticator

OK, the MT shares the lubrication of the differential with the transmission gears, the differential is a hypoid gear, and would "like" GL5 lube, but GL5 is too slippery for the transmission synchronizers, so Synthetic GL4 is the required specification.

Ok, but would the Redline 75W90 NS oil without friction modifiers (designed for synchronizers) be acceptable or better than MT90/MTL?

**diagnosticator** · 04-25-2008 11:18 AM

Originally Posted by Splattj

Ok, but would the Redline 75W90 NS oil without friction modifiers (designed for synchronizers) be acceptable or better than MT90/MTL?

I don't think so. Because a GL-4 is specified by Audi, the higher friction in the diff with GL-4, compared with GL-5 is less important than proper synchro function assured with GL-4. I recommend asking Red-Line what they advise regarding the Audi's hypoid diff and synchros and shared lube. I think MT-90 is prefered here...