hey guys i recently drained my 4 speed and refilled it with the crc brand gl-4 yellow safe 80w-90 gear oil, im pretty sure the old oil was gl-5 put in by the po, that shit was blacker than black, before i changed it third gear would grind a bit when i wound out second and shifted, now its smooth as a babys ass, i didnt realize how big of a difference it makes!!!! i am going to be putting in my new engine and my 5 speed soon and i just wanted to kind of flush out the 4 speed before i stored it, if any of you have gl-5 or even if you have a gl-4 thats not yellow metal safe GET IT OUT!!!!!!!!!!! that shit will ruin your trans, dont go to a parts house and talk to anyone about it, they are all idiots, find it yourself so you know you have the right shit.