I decided after 210,000 miles to change the manual transmission fluid on my 88 Audi 90 FWD. Bought some 70W90 full synthetic Quaker State GL-5 at the local auto parts store, put it in and immediately had a problem. The shifting was rough, would not syncronize. Suspecting that I screwed up, I called up Red Line Oil's 800 number and got some good advice. My car needed GL-4 spec, Redline's MT-90 oil which has some "friction modifiers" to allow for easier shifting, helps syncronizer work better. Redline rep said the GL-5 was too slipery.

After a search, I found the Redline at a speed shop. Drained out the Quaker State and put in the Redline and everything is back to normal. Good smooth shifting.

I learned this one the hard way, but at least I flushed with the double change.

I had the same problem with my 1986 Coupe's gearbox. Put in some synth oil, caused shifting problems! Replaced hypoid with regular, non synth oil, shifting back to normal.

is the redline GL-4, MT-90 the proper gear oil that you are supposed to use on the 1993 90's as well?

'94 owner's manual specifies 75W90 GL-4

'94 90 cs quattro
Mike