[mik13usa]

standard gear oil in these transmissions is just a bad idea. Period.! The manual may say use GL 4 BUT... The cars originally came with GM synthetic Synchromesh. How do I know? I worked at one of those oil change places for years, many years ago. Any time someone would change the oil to the Manual reccommended they would begin to have problems. It is just like Blake said, the GL is to slick, it does not allow for the proper friction element to engage the gears properly. Again this is only my opinion. And any one who swears that Redline hosed their tranny, I would love to see them personally. I have done years of research about the subject, and have yet to see the transmission ever built NOT perform better with a synthetic Esther based gear lubricant.