Trans T5 gearbox oil
generalmoto
Jeeper
GM friction modified synchromesh was the best one I tried. After rebuilding a couple T-5 ’s with my AMC 304 I bit the bullet and put in an AX15. The T-5 is too light duty for any kind of power. Do not use gear oil as it is too thick to lubricate the needle bearings and ATF works if you don’t mind grinding every gear