gear oil

Once again. Early FSM specified SAE 90 gear oil, ATF in colder climates. Later ATF. I believe Dartnut when he says he had problems with synthetic. I've rebuilt enough 4 speeds to tell you, I can see more wear in an ATF gearbox. I see no advantage to synthetic lube and have heard of problems. Racers count every .01 of a second and do not have long term maintenance issues. SAE 90 will keep everything lubed and shifting as intended for 2 to 3 hundred thousand miles.