I feel like I should be able to find an answer to this question, but apparently my search skills are subpar. The shop manual for my 1950 3100 says that I can use SAE 90 gear oil on both the tranny and the rear end. I believe I currently have the SAE 80w-90 GL5 in the rearend because that's what I could find. If that's not a terrible idea, could I also use that for the tranny?
Also, is there a way to know how much fluid is already in there after draining the tranny. the manual says capacity is 6 pints. i haven't yet measured how much much fluid came out, but it didn't seem like 6 pints. I don't want to over fill. Thank you.
You'll find lots of discussions in the archives about transmission VS rear axle lube, and plenty of opinions. GL5 lube probably isn't a good idea in transmissions like the SM420 4 speed- - - - -the gears are big, heavy, and have lots of inertia, and GL-5 is just too slippery to let the synchronizers function properly. GL-1 straight 90 weight would be a good choice there. It's also plenty good enough for rear axle lube, plus it's WAY less expensive than the fancy Moose Juice most local auto parts stores sell. In the southeast USA, Tractor Supply sells a straight 90 weight gear lube that's used in Ford N-series tractors- - - - -just like the original stuff Chevy ran in the 1940s, 50s, and 60s.
Fill transmissions and rear ends level with the bottom of the fill hole in the housing with the vehicle on a flat floor- - - - -that's the recommended fluid level. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
The gl5 is good for the rear axle but recommended for the transmission is gl4 due to the brass parts in the transmission .Up were I am from gl4 is non existent .i have found that Canadian tire in Canada has motomaster gl4/gl5 and is safe for yellow metals.
I have used SAE 90 wt from Tractor Supply in my 53 3100 in trans and rear axle. Currentl I have the GL5 in both trans and rear axle.My trans shifts much smoother with the GL5. The 3 speed takes a 1.5 pints and 4.5 pints for the rear axle. Follow HRL advise on how to fill.
