somewhere I remember advice about oil for standard transmissions for my '49 Lincoln. This is a 3-speed with overdrive and I recall the writer advising against oil that could ruin old style bearings. I don't know if we can use synthetic oil in these old transmissions or just what we should use so I'm soliciting advice from those wiser than me. thx
GL4 has the protection for brass parts in it, I know GL5 does not and never heard of GL3 until now. I would stick with a mineral-based oil over a synthetic in old cars.
Penn Grade (new name for Brad Penn) makes a GL-4 mineral 80-90 that Summit Racing sells, seems to work well in my Ford toploader 4 speed.
The last TREMEC TKO 500 I installed recommended this! Summit sells AC Delco Synchromesh for about 25 bucks less per quart. If I pay $35 for a quart of anything it better taste good on ice.
Holy Cats, Billy! Thirty-five bucks per quart! What is this stuff, liquid gold? Squirrel seems to be on the right track as I recall the discussion being about brass or bronze parts.
I used that when I first put my car together with the Muncie. After I broke it and had it fixed back in May, my local speed shop had some Richmond GL4 and I used that.
One guy I hang out with swears by the GM Synchromesh, but the label really gives no real description on what it is as far as a grade goes.
I Use Smitty's Super S GL1 Gear oil. That is what I have always been told to use in old transmissions. It is mineral oil based and will not eat the brass parts like in a 39 Ford trans or other early trans missions. Yes it is expensive per quart, I think it was like 15 dollars a quart, but for some reason a 5 gallon bucket 140 GL1 only cost $75 dollars from my local parts guy, and he had to order it.
http://www.smittysinc.net/catalog/gear-oils/gl-1-gear-oils/super-s-sae-140-gl-1-gear-oil-154575070/ this is what I would recommend for an old trans, or whatever weight you may want.
My NP3500 and the NP4500 use Synchromesh. From 90's Chevy and Dodge 1/2 and 3/4 ton trucks. The FWD manual cars also use it. https://www.pennzoil.com/en_us/prod...6b2lsLzIwMTZuZXdzbGV0dGVyLz9sb2NhbGU9ZW5fdXM=
I know this sounds crazy... but, has anybody thought to look and see what the manufacturer called for in the shop manual under "lubricants & capacities"? Back then 50w oil was commonly used. I understand hypoid gear oil like 80/90 is often used today in both differential and manual gearboxes. It has sulfur or something that is supposed to be hard on brass synchros. Maybe.. It must take a while though, more than 20 years, by my count.
FYI GL-_ gear oils, everything below GL-4 and above GL-5 are obsolete. If you're using GL-1, that is almost straight mineral oil with a some anti-foam and rust & oxidation inhibitors, no anti-wear. Not really great stuff for transmissions. https://www.lubrizol.com/Lubricant-and-Fuel-Additives/Driveline-Additives/Axle-Oil/Specifications
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