5w-30 or atf?
 

ok so i have a 86 non wc t-5 from a firebird. i now normally to use atf in the trans but theres a gm metal tag, no joke, zip tied tot he trans. on the tag it says gm, some long number, then 5w-30. thoughts?

Re: 5w-30 or atf?
 

GM themselves flip-flopped among gear lube, ATF, and motor oil, several times during the life of that transmission, and in various different vehicles. I don't know why, since all the parts are ABSOLUTELY IDENTICAL IN EVERY WAY regardless of what lube they recommended for each given application; but I suspect it was some kind of compromise among the beaurocracies at GM responsible for gas mileage, warranty, noise, and leakage.

I've used practically every petroleum-based product there is at one time or another in those, and they still fragged. I wouldn't get too wound up over it.

Best results I ever had in one of those POSs, as far as shifting, was from half & half ATF and synthetic gear lube.