Transmission oil

J

Jim in S.C.

Member
Can you use the 600 wt. oil in a 1939 topload transmission? I am just wondering if it would cause any problems. I just want to stop some of the leaking at the back of the transmission. It is leaking around the lower of the two shafts that go in from the back end. I just don't want to tear it down to fix it. Too
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old and too tired!
 
I had oil leaking from my 1950 Ford Transmision,I put in some "STP" oil treatment ; this swelled up the trans seal and stopped the leak, also used the STP in the flathead motor it also stopped the leak in the rear oil seal for a time so added more at oil changes beats tearing everything down for a rebuild on an old motor and Trans ... JMHO.... Da.:)
 
Jim, the 600 wt. is too heavy for the synchronizers in the '39 box. I use 80-90 in mine and it works fine. Yes it leaks, but it shifts great. Ed
 
Compromise ... I use 140 in my transmissions. Both have "39" gears. Both leaked with 80/90. One stopped leaking completely with the switch. I had rebuilt it and used a sealer around the shafts which didn't stop the leak. The 140 did the trick.

The other slowed down considerably. This transmission was in the car when I bought it and sorta poured 80/90 oil out. Switching to 140 really slowed it down, PLUS 2nd gear synchro had been catching a little metal and completely smoothed out with the 140.

140 shifts great in Florida and should in SC, too.
 
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We take the sealer a step further. Of course, a gearbox in our shop gets oven baked, media blasted, and pressure washed before assembly. So everything is bone dry. Beside using the RTV sealer at the front and back of the case where the shafts come thru, we also put RTV sealer inside the opening for the lockpin AND some on the lockpin itself. We slide the lockpin into place and let it sit overnight. I found that many of the "leakers" were also leaking out the lower end of this lockpin. We put the cotter pin on the lockpin the next day. Seems to help.

The old 600W gearbox goo was not designed for the 1932 and newer transmissions. We don't recommend it. I also do not recommend using the new synthetic gear oils. They seem to find the tiny cracks and openings too easily. Get GL1 if you can find it (probably have to order it). Hoop is right in using the heavier 140W oil but keep in mind that if you want to drive the car in cold times, the 80-90W oil would be better.
 
What weight oil would you use in a 50 Ford transmission overdrive? Would you use the same in both front and rear of the ******?
 
Ford recommended 80W for winter and 90W for summer on the standard 3 speed and overdrive trannies. Capacity for 49 and 50 Ford overdrive trans was 4-1/2 pints combined. They recommended a "mild EP gear oil" (in their words from the Ford service manual).

You were supposed to drain the gearbox and the overdrive unit from their own drain plugs. For refilling, they said to refill thru the gearbox only. There is a common passage between the units, but if you do it that way, be sure to get the full amount in. I recommend waiting overnight and re-checking the level to make sure it hasn't gone down due to settling into the OD side.
 
Lubriplate SPO series gear oils are GL-1 mineral types. If you have a Purvis Bearing shop near, they are a distributor. Restoration Supply company is also a distributor. SAE grades up to 250 are available but 140 (SPO-277) should do the job. The GL-4/GL-5 oils that are most prevolent these days have extra pressure additives that can corrode the bushings in the older transmissions. You can use them but they will slowly degrade the yellow metal parts. They will work fine in a rear axle though since there are no bushings in there.

Kerby

PS: Nearly all the EP additives used today contain materials that actually eat there way into a metal surface to provide scuff resistance albeit microscopically. Most have sulphur or phosphorous and both are mildly acidic in the EP formulas
 
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I put 600W in my 40 box and found it leaked just as well as 90. 600W is apparently similar in viscosity to modern 140, from what I've read. I think the only real solution is the o-ring seal approach for the shafts. Or just plan ahead and put a drip pan under it. As someone pointed out on here or the HAMB, those old concrete driveways with the two strips for the wheels and grass or gravel down the center made a lot of sense back in those days!
 
Three O ring grooves in the case stop it for good. One at the front, 2 at the back just forward of the lock pin holes in the bores for the idler gear and cluster shaft. Some lube on the shaft and O rings and the shafts slide right in. No RTV to smear around.
Of course this is done anytime you have the transmission apart, not a help for a leaker in the car.
 
GL4 is usuals good with bronze syncos, GL1 is not very good for helical gears. The EP additives won’t corrode the bronze anymore until the oil reachers 350 degrees witch it never will but it coats them with a protective layer that gets torn away and takes bronze with it witch will destroy yellow metals fast
 
Mineral GL1/GL3 in the gearbox....GL4 in the rearend.
GL4 even if they state it´s redmetal safe makes the syncros less good reacting with the metal surface if lucky and eats away on them if unlucky....
Another area where overdoing it isn´t always a good thing....
 
Rudolf,thanks for that useful info on what temp the later gl5 oil will attack the bronze parts,
I reverted to using GL5 oil in my trans as we have trouble getting the gl4,
My trans do a lot of miles towing and the trans has stayed good
Lawrie
 
Lawrie said:
Rudolf,thanks for that useful info on what temp the later gl5 oil will attack the bronze parts,
I reverted to using GL5 oil in my trans as we have trouble getting the gl4,
My trans do a lot of miles towing and the trans has stayed good
Lawrie
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I am saying don’t use GL5, use GL4 or you might destroy your synchros not by corrosion but by them being worn away by sulphurous coating being deposed then ripped off.

Someone I know sed it takes about a week to kill the synchros, but possibly the oil you have is ok with the synchros?
 
A lot of GL5 suppliers are now claiming they are yellow metal safe. Not sure I would trust them, but that is the claim. I stick with GL4 just to be on the safe side.
 
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