Gear Oil for T176 and Dana 300

Gear Oil for T176 and Dana 300


Crawford, CO
1983 CJ-5, I6 258, T176, Dana 300, 3.54 AMC 20 and Dana 30, purchased 4/12/11 with 79000 miles on it.
I want to change out the transmission and TC oil in the 83 CJ5 I recently purchased as I dont know how long it has been in there. I have conflicting info on going with mineral oil or synthetic. Cost is an obvious con for synthetic, what other considerations/recommendations do you guys have?
I run a good 80w90 oil and add some Lucas oil treatment to it.
I've heard people say they got leaks after changing to a syn. oil in older vehicles. Never happened to me though.
I use good old dino 80-90 in my d-300, and it still leaks :laugh:
I've done a lot of research on this the last few days. Turns out that syncromesh transmissions like the T176 really should have a less viscous fluid. I got that from Tremecs website and a few other references. Apparently the bearings need a thinner lube. I dont know what the owners manual recommends but apparently the 83s came from the factory with ATF in both the tranny and transfer case. Also you do not want to use a GL-5 gear oil because it is high in sulpher that will corrode the brass parts. It is getting increasingly hard to find a GL-4 rated gear oil. Think I am going to try Amoils MTF in the T176 and Redlines GL-4 75-90 in the Dana 300.

The way I see it when these things came off the show room floor they only had motor oil and gear oil so that is what I use.With the exception on Limited slip and locking difs.I am the same way with my old 1972 Harley.60wt motor oil and 80w90 in tranny.These older mchines dont like synthetic stuff.

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