Posted 8/20/2013 01:34 (#3277228 - in reply to #3277200) Subject: RE: What oil should i use for tranny and rear diff on 1977 GMC 6500?
Somerville, Indiana
50W synthetic will shift a lot easier in cold weather, and run cooler in hot weather for the transmission, but stay with something like 85W90 for the differential...They say the hypoid gears don't like 50W oil.