The Stovebolt Site Forums The Shop Area Engine Shop Lubrication Question

Talking the other day and got on the subject of transmission lubricants for standard trans. Mechanic who has a local shop says Amsoil is used a lot for this and is real thin, like a 10w. Says Nascar is using this thin weight oil in their racecars. Doesn't seem quite right to me and know all the manuals and past experience say use 90w in the trans and rearend. Would like to hear what you are using in this area and your opinions.
Bruce

Running 80W-90. Don't forget, Nascar doesn't use production parts, all the gearboxes are built to very tight tolerances. And the newer manual trannies use ATF for lube. Don't try it in one of these old gals unless you are an expert at arranging drip pans under your truck!

I can relate to drip pans under the truck.

Drip pans! Did I read drip pans. This was the reason I posted this question. Recently rebuilt 3 speed trans came from the builder with the thin oil in it. After a few days I notice oil spots on the driveway. Seems its coming from the clutch assy cover plate. Will be draining the trans and using the heavier stuff this weekend. Hopefully this will stop the mess. Thanks for the info.
Bruce

Wish I could add some positive information to this, but in talking with an elderly gentlemen who built 35 to 46 GMC's at the factory, he said "Boy, that truck of yours leaked the day that it got built,get over it". Been a real fan of drip pans.

My manual states to use 50W detergent oil (49 GMC) in the three speed. Don't know what your tranny is but it also states NEVER to use hypoid oil. Ruins the innards!

Standard 3 speed trans. No OD, nonsynchro 1st gear.
Bruce

Dang! I just learned something. They must have used babbit bearings, cuz hypoid oil will ruin them.

Fred,

Actually, I think there are sulphur compounds in the Hypoid lube that attack the bronze bushings inside the tranny...

At least, this is what I THINK I read on the AACA website....

Have always read SAE 80-90 for the manual truck tranny....and whatever you're putting in the rear end should have an EP rating ("Extreme Pressure") for the hypoid ring & pinion.

The ONLY antique trannys I've ever seen use less than gear lube were the Chrysler semi-autos that used SAE-10 oil.

If some rebuilder tells you "light oil" is okay in your 'Bolt's tranny, ask him if he'll give you a warranty on the tranny which will include free rebuild-replacement for at least 50,000 miles!

wbkinsey,

What year transmission do you have (is it GMC or Chevrolet)?

For what it's worth, the USA and Canadian Shop Manuals specify Multi-Purpose SAE 90 lubricant for 1954 standard 3-speed, heavy duty 3-speed, and four speed.

Tim

TC: Trans is the standard Chev 3 spd in a 1959 1/2 ton.

Ron: I agree with your statement but we don't get sub-zero temps here in GA

Will be going with the 80w-90 or straight 90w.
Bruce

90 weight gear oil and 50 weight engine oil are the same viscosity, the numbers are different to avoid misuse.On the websites of some major lube makers is the warning about using modern GL-5 gear lubes in older gear boxes,additives attacking yellow metals(brass and bronze?) as mentioned above.If the gear box was designed to use motor oil,or a light oil then it should be ok.Spicer used to recomend the use of 50 weight motor oil ,not gear oil in some medium duty truck trannies.Many modern gear boxes use thin ATF as a lube.The NP 3500-4500 series transmissions use a light gear oil.The NP A833 4 spd OD tranny is supposed to use ATF, but Mopar guys say to use a 75-90 gear oil for less noise and longer life.

Looking at my original (read old) 1949 GMC manual on lubrication. Says that the tranny take a "ES" special engine oil. "SAE 50, ordinary gear oils are not satisfactory, detergent dispersant properties, oxidation resistance and anti-foam."
Used it in mine. Whined when I got it, still whines but what the hell, at least it's full and lubricated. :p