I have been planning on replacing transmission gear lubricant on my 97 1.8TQM and got the little tool and picked up 3 qts of Mobil 1 75W90 Fully Synthetic Gear Oil. I bought it all at Autozone and didn't know the difference between gl4 and gl5. I was just planning on following Sandman's DIY. I believe the Mobil 1 I got is GL-5. His DIY makes no mention of this number. Should I return the Mobil and order Redline stuff online or is the Mobil gonna be fine? I have searched and haven't been able to find a concise answer.

 

any help?

 

The only mentions of GL-5 on the back are in two places.

"Outstanding protection of hybrid differentials where API GL-5 quality 75W90 oil is recommended."
and then
"Mobil 1 Synthetic Gear Lubricant 75W90 exceeds the performance requirements of API GL-5."

 

alot of people are running that you should be fine. i on the other hand went to audi and bought 100.00 worth of stuff for the trans and rear diff. after the fluid change, my transmission is 100% smoother, but still a bit stiff in 2nd gear when cold, which seems to be a common problem

 

100% smoother? wow. that good huh? i've always wanted to do this.

 

yea, contrary to popular belief, synthetic over time will loose its lubricity. i have 95K on the car, and i wasn't really having any problems, (except for the stiff cold 2nd) i noticed a difference almost instantly. the trans wasnt low, and the fluid came out a honey color (about the same the new stuff went in) i was pretty happy knowing that the oil i put in worked good. i may do mobil 1 next time, but figured the 'real stuff' was worth it. i have also read that some fluids may be too 'slick' and cause problems not speeding up the syncro rings properly (or not slick enough, causing them to spin too much) again, don't take that as gospel, thats just what i have read

 

whats the process for doing the rear differential? im sure there is a write up somewhere... someone wanna throw a quick link in here. this could be a quick easy thread for search purposes for people.

 

http://www.audidiy.com/b5a4.html