What Weight Oil?

B

billybronco1

Well-known member
What weight oil should I use in my transmission and rear end on a 1936 sedan? I used the 600 in the Model A is it still the same for the 36? Who has the best stuff these days?
 
The 600w topic has been discussed several times here on the Barn. It is a steam engine oil with little to no additives and is around SAE 140 viscosity (ISO VG ratings vs SAE ratings). Ford never recommended the 600w (which is a brand name for the Mobile steam engine lubricant) for use in Ford v8 era vehicles. Because of the lubricates available at the time, Ford recommended a Summer and a Winter viscosity based on the operating environment. Modern multi-viscosity lubricants are the way to go IMO.

The "w" used in SAE viscosity ratings stands for "winter". Lubricants are rated at two different temperature ranges, the "w" being how the lubricant flows at the winter temperature rating. The number before the "w" is the flow (viscosity) measured at 0 deg F and the number after the "w" is the flow (viscosity) measured at 212 deg F.

Gear lubricants have GL ratings mostly based on the additives, EP (Extreme Pressure) being the major concern on transmissions with synchos. Transmissions and rear axles can use the same lubricants IF it is one with a lower amount of EP additives. The components that are effected by the EP are referred to as "yellow" metals and this issue is not specific to Ford V8 era vehicles. Later model manual transmissions (60s, 70s, 80s, etc) have the same requirements.

GL1 does not contain EP additives, GL2 is obsolete as is GL3 (it is available, but not easy to find). GL4 is the modern Mild EP gear lube and GL5 has a larger EP component.

Ford (this is per the lubrication charts) recommended Mild EP lubricant for the rear axle, which would be GL4 in modern ratings, and straight gear oil, which would be GL1 in modern ratings. In later years Ford changed the recommendation to Mild EP lubricant for both the transmissions and rear axle. As the internal components of the transmission are the same, this was, IMO, just a change in Fords recommendations for their synchro transmissions.

The SAE viscosity you use depends somewhat on how you like the "feel" on how your transmission shifts. Different people like different viscosity lubricants. You can use the same lubricant in both the transmission and rear axle as long as you use GL4. Or, you can use GL4 in the transmission and GL5 in the rear axle. IMO, only use multi-viscosity lubricants.
 

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So that is a lot of detailed information, what do you use? Sounds like any SAE 140 weight GL4 rated to me in both locations will work.
 
Finding a straight GL4 SAE 140 is not as easy as I thought almost everything is multi grade unless I want to buy large quantities. Any other suggestions?
 
I've run GL5 in my 49 for 40,000 miles and when torn down to fix a leak there was no indication of wear on the brass. Wile it will affect the yellow metals my understanding is that it is not until the oil reaches temps our transmissions will not see.
 
Thanks Frank, but I think there could be quite a bit of difference between the 39 and 49 ****** components I would be concerned with using GL5. And do you use a straight 140 or multi grade?
 
Looks like this is used by others Sta-Lube P/N SL24238 API/GL-4 Multi-Purpose Gear Oil SAE 140, 1 Gal I will have a life time supply but this seems to be the stuff for ******, rear end and steering box, would you agree?
 
billybronco1 said:
Looks like this is used by others Sta-Lube P/N SL24238 API/GL-4 Multi-Purpose Gear Oil SAE 140, 1 Gal I will have a life time supply but this seems to be the stuff for ******, rear end and steering box, would you agree?
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That'll work just swell. Allot of guys use cornhead grease in the steering box if you have issues with the 140 disappearing from there. It's a NL00 grease, solid when cool but liquid when warm.
 
Will D said:
That'll work just swell. Allot of guys use cornhead grease in the steering box if you have issues with the 140 disappearing from there. It's a NL00 grease, solid when cool but liquid when warm.
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Okay, Sta-Lube P/N SL24238 API/GL-4 Multi-Purpose Gear Oil SAE 140, 1 Gal is on its way, Amazon best price I could find at $30
 
The SAE 140 will work fine in the steering box except for the leakage! These steering boxes just seem to want to leak. You can try the 140 and see how it goes, but if you do have leakage, cornhead grease is a good way to go, it is sold by John Deere or online.
 
JSeery said:
The SAE 140 will work fine in the steering box except for the leakage! These steering boxes just seem to want to leak. You can try the 140 and see how it goes, but if you do have leakage, cornhead grease is a good way to go, it is sold by John Deere or online.
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I just looked in the steering box, it is almost full and it has a clear redish liquid in there, does not leak, looks super clean.
 
billybronco1 said:
I just looked in the steering box, it is almost full and it has a clear redish liquid in there, does not leak, looks super clean.
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I would leave it alone then . I have finally learned ( I think ) after 50 yrs. in the hobby not to fix stuff that ain't broke . - F F
 
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