: What happens if you use 80W90. Will the tranny or rear end be damaged?
Dan, It's probably OK to use 80W90, it's just too thin to stay put. The tranny doesn't have seals as they have today but rather it has slingers which the oil still gets by. The thick stuff stays put. Haven't been into the rear end but it probably uses the same seal methods of the day, I would be watching for leaks at the axles. GW