Transmission Lubricant

[PatS....]

Can anyone tell me the correct lubricant for the transmission on a 1946 Fargo 3 ton with a 5 speed transmission??

Thanks

Pat

[grey beard]

To my best knowledge, all truck transmissions and differentials used standard 90 weight gear lube, back in the forties and fifties. It has only been in the late sixties and seventies that vehicle makers began to specify - or have available - multi viscosity gear lubes. The heavy truck industfry and I'm sure industrial stuff like Merle Coggins is familiar with often use much heavier lube, like 180 weight. The trucking company I worked for back in the seventies switched from 90 to 189 gear lube in their differentials, and I never saw another leaking differential after that, as long as the housing vents didn't clog up. When that happens, they will all leak at the weakest point. JMHO

[CaseyJoeS.]

Only other thing is that the gear lube should not be a GL5 rated gear oil. Use a GL4. The GL5 contains additives that alow it to better handle extreme loads. These additives are corossive to brass and bronze supposedly. So just make sure the bottle you get is a GL4 and not a GL5 rated gear oil. I dont think that Valvoline makes a GL4 gear fluid anymore but Im pretty sure Pennzoil does along with several other companies, such as Red Line Oil.

[PatS....]

Thanks Dave, CaseyJoe...great info...should help alot. I gave the truck to my nephew and he has it almost ready for the "new" engine to go in, then some wiring and a test fire. I'm just the consultant on this one.

Nice to see a young 'un so excited about an old truck...well, he's 28 but to me that's still a kid.

Gawd I feel old

[Merle Coggins]

That's interesting info on the GL5 incompatability. I'll have to look into it. I currently have GL5 80w-90 in my axle.

Dave, I've never worked 190 wt. oils. The heaviest oils I've seen is a 85w-140 gear lube.

Merle

[CaseyJoeS.]

When I changed the transmission fluid in my car (1989 Jetta) I noticed it specified a GL4. I noticed everything on the shelf was rated GL5 though. So I did a little research online and that was the only difference I could really find between then was additives and supposedly the ones in the GL5 meant for newer vehicles could corrode brass or bronze parts.

I'm 18, cant wait till I can buy the 48 pilot house i'm looking at. I would have bought it already (me and the seller agreed on a price) but he hasent been at his house lately where the truck is or answered his phone. So i'm just waiting till I see him again. I'm wondering if he had a problem as its been nearly three weeks now since i've seen or heard from him.

[grey beard]

Sorry, Merle,

I mispoke. Checked my jug, and it reads 85-140. It also reads, GL5, GL4, GL3.

Brand is Coastal. Vendor is WalMart. Sorry about that.

The 180 wt. gear lube was used in our semi fleet, over 30 years ago. Memory says it was not a multi-vis, just a straight weight. Sure did dry up a lot of differential leaks. We did not use this stuff in transmission gear boxes - shifted too hard in cold Indiana weather.