I need to drain and replace the trans oil in my coupe. It is a straight '39 Ford box. Does anyone use Lubriplate SPO oil in their trans? This is supposed to be the right stuff for early trans parts as it does not have the high sulfer cotent. If so, what version/model # best matches the 85-140 weight specs? I know this sounds like a silly question, but what is the trans case capacity? I will be pouring the oil down the shifter hole, as the floor is finished and glued down. This might answer my question, but does every early Ford trans case have a fill capacity plug? Thanks, Jay
Yes, there should be a fill hole on the side of every early ford trans case. I believe the fluid level should be a little below the opening, not running out of the hole. Napa also sells a gear lube that doesn't have sulfur compounds in it.
I just bought and installed some Sta-Lube GL-4 (good for trans with brass in it) gear oil from NAPA. I used half 90 and half 140 straight weights. I'd read in one place to use 90 and another to use 140, so I split the difference. It took me about a half gallon, but I'd pour slow in case that's too much. Takes a while to flow around the gears and find a "level". I had the top off the trans so I could see when it reached the plug.
OK. So I found 90w trans oil at Tractor Supply Company (TSC) specifically for early Ford tractor transmissions. It is the non-corrosive, mineral oil (GL-1) recommended for the tractor as it has brass bushings and synchros. Anybody use this in their trans? I would think that if it works and is designed for a Ford tractor, it would be just fine for a '39 3-speed box. Any opinions?
Go over to the ford barn and do a search... There is a lot of info on 600w oil that was originally specified.. However there will be a bunch of different opinions... I used 85/140 and Lucas trans. Took 2 qts +\-.... good luck.. Btw 600w does not mean 600 weight, it was merely a spec# for ford.
Find a good brand 90 weight viscosity GL-4 and leave that tractor lube alone, as it's for low speeds. GL4 is brass compatible and has more modern anti foam additives, etc. than that GL1. Stay away from GL5 rated gear lubes as they do tend to attack the brass synchro rings, and also are so "slick" that the rings aren't as effective at their job of synchronizing on shifts. I use Amsoil GL4 rated 75W-90 Synthetic Manual Trans Lube in mine. But I should disclose that I also sell it.