I just bought some MT90 for my tranny and some 75W90 for my differential on my '87 TII. I've heard really excellent things about Redline, but what kinda scares me is the Haynes manual says to use GL-5 type fluid for the tranny and MT90 is GL-4. I'm kinda scared of ******* it up. People say (on this forum) it make a world of difference to switch. What do you guys think?

 

ignore it. I've used MT90 in my tranny in my old NA FC. It worked just great. i'll be using MTL this year on my turbo II because i dont plan on the car ever seeing winter.