VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc GL-3 for 1950 transmission

Is the GL-3 manual transmission lube sold in auto stores ok for 1950 three speeds? manufactured by Penzoil, no weight given. Label states it's acceptable for most GM products

Most of the people on this forum use GL-4 for transmissions, typically in 75W-90 or 80W-90 weight.

The GL-3 is an older API designation which has been superseded for quite a while by GL-4 (not sure when). I would be surprised if you can even find GL-3 gear oil.

Interesting that there is discussion within API about retiring the GL-4 designation

sorry it took a while to get back here, works been good. The GL-3 in question, if memory serves me, which sometimes it doesn't, I purchased it at Federated. If not there, then Advanced. The question remains, Is it suitable for 1940's, 1950's manual trannys? Be patient, it may be a while before I can respond, work keeps me occupied, hence the term occupation.

the "GL" rating system has to do with suitability as gear lubricant, and specifically as hypoid gear lubricant. It is fairly useless in determining suitability for use in a manual transmission with synchronizers. More information would be needed to even make a reasonable guess, like the datasheet for the oil in question.

I think I remember seeing some Fiats in the 70s that specified GL-3 for their synchronized transmissions, at least in the USA. It is probably fine.

If it were me, I would either use I would use something MADE for synchronizers, like one of Redline's oils (MTL, MT-90, or 75w140-NS, in order from thin to thick) or GM Synchromesh, or Pennzoil Synchromesh. Those last two would be thin like MTL. There is some concern of thin oil leaking down into the rearend too fast.

But, if it must be something more traditional, there are plenty of guys in here who can tell you what works well if you ask that. Get a specific brand and type recommendation though. Going by GL rating and weight is like throwing darts IMHO.

it is the Pennzoil Synchromesh.

IMHO it would be fine. In fact, it is what I might use.

The only concern, as it is lighter than what GM used back in the day, is that it might leak into the rearend faster. Keep a close eye on the level for a while.

Also, if you rely on the oil to stop your unsynchronized first gear when you push in the clutch at stoplights, that is going to happen slower. I just tap second or third before going into first.

FWIW this subject has come up before, and there are forum members who have these transmissions shifting just fine on fairly ordinary gear oil from the parts store. It doesn't necessarily need something special.