ive heard to use atf from some people but in most books i see it says a heavy weight oil which is it?

I was always told and have always used 80-90 wieght oil, I have never had any problems with any of my manuel transmissions.
Later, Garrett

the service manual and if you call the dealer they will all say to use atf. comes stock with atf.

but I was told to use straight 30w oil, thin enough to flow but better protection for the bearings.

i believe the NON WCT5s take gear oil and the WC T5s take ATF. with that said i'm running amsoil gear lube in my WCT5 with no problems so far. i have read or heard that gear oil will hurt the syncros, but i'm willing to rebuild it when and if that happens for the extra bearing and gear protection i get from the gear oil.

I am not sure if I understand, WCT?? I do not know trannys enough sorry.

WCT is world class tranny, came in v8 cars, think it was first made for ford cause the regular T5 could not handle the torque.

So they rebuilt the whole thing and came up with a WCT.


"T-5 started life in 1981 as a 4 cyl transmission. Ironically, it first saw life on the Mustang as mated to the 5.0L. The original SROD was considered not strong enough to keep up with the growing output of the 302. In '85, the World Class (WC) version of the T-5 was released for the 5.0L, whereas the base T-5 remained on the 2.3L. There are differring opinions about which is better. The WC T-5 has better torque handling capacity, but it's real weak spot is in the 3rd gear cluster. As the tranny is put under load, the case flexes and causes bind in the 3rd gear cluster... with failure as a result. "

big weak spot in a regular T5 is 5th gear, but there is a part you can buy to stiffen the case. but who races in 5th???