transmission lube

I had a Model A come to me with some form of "liquid grease" in the transmission, differential, and steering box.

The bearings in the transmission were roasted from lack of lubrication, and the axle bearings in the diff were shot. The pinion bearings looked OK for some reason, just worn.

Mitchell Manufacturing makes a couple neat add-ons that will help with transmission fluid leakage.

https://mitchelloverdrives.com/products/mitchell-oil-seal/
 
Transmissions, steering gear boxes, and differentials need a specially designed lubricant that has the ability to "climb" the gears while rotating against each other. This "climbing" effect allows the lubricant to pass from one gear to the other, and so on while moving. The same principle is true with ball and roller bearings. The manufacturers knew this and specified and a gear lubricant to be at least in a semi-liquid state to do just that. If grease is used, the grease is squeezed out from between the teeth (or bearing surfaces) with nothing to replace it. Once the lube is gone, the heavy shearing loads against them doesn't take long for gears and bearings to rapidly wear themselves out.
 
There is no secret magic stuff to put in a transmission to fix it. There are no shortcuts. To fix the transmission you will have to take it out of the car and rebuild it or send it to someone to have it rebuilt.

Modern gear lube has additives to extend the life of the gears and bearings. The modern gear lube is much better than what was available in 1930. Use 85W-140 GL5 gear lube. The only exception would be if you have snychromesh, in which case I would recommend 85W-140 GL4.
 
nkaminar said:
Modern gear lube has additives to extend the life of the gears and bearings. The modern gear lube is much better than what was available in 1930. Use 85W-140 GL5 gear lube. The only exception would be if you have snychromesh, in which case I would recommend 85W-140 GL4.
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I am certainly not an expert on oils but it is my understanding that all modern GL-5 Gear Oils are safe for yellow metals

Steve Mitchell recommends 85w140 GL-5 Gear Oil in both his O/D (which has synchros) and Synchro Transmissions.
 
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Hey,


I soldered two pots out of sheet metal and attached them with magnets. It works without dripping.


I use a very thick 1200 steam engine oil.
 

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Master Cylinder. I found some brass dust in the oil I changed out of the Mitchell overdrive. I think they are making a mistake recommending GL5 and should be recommending GL4. The GL5 does too good of a job of coating the parts and when it wears off, as it is designed to do, it takes some brass with it.
 
GL-4 85w-140 Gear Oil doesn't seem all that common. Companies like Lucas don't even offer GL-4. Maybe I am looking in the wrong place?
 
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nkaminar said:
Master Cylinder. I found some brass dust in the oil I changed out of the Mitchell overdrive. I think they are making a mistake recommending GL5 and should be recommending GL4. The GL5 does too good of a job of coating the parts and when it wears off, as it is designed to do, it takes some brass with it.
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Neil, Thanks for the info on the GL-5 Gear Oil in the Mitchell Transmission. Do you have a preferred 85W-140 GL-4 gear Oil you recommend?

No, I'm not trying to start another "oil" war. I seem to be having a hard time finding a 85W-140 Gear Oil. Most are GL-5.

SAJ said:
Here is a link to a good explanation about GL4 and GL5 oils and their effect on brass or bronze synchro rings.http://https://www.machinerylubrication.com/Read/30366/gear-oil-applications#:~:text=So%20while%20an%20API%20GL,are%20made%20of%20softer%20material
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SAJ, your link doesn't work. Fixed it here:

http://https://www.machinerylubrication.com/Read/30366/gear-oil-applications#:~:text=So%20while%20an%20API%20GL,are%20made%20of%20softer%20material
 
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Master, No preference. At the auto parts store where I shop most of the oil is GL5 with maybe a couple quarts of GL4. If you cannot find it locally, try the internet.
 
I run Lucas Oil Stabilizer. By FAR the smoothest shifting over 80/90, 140, 600w, and others. Been running Lucas for 10 years now I think.
 
OK, just curious. What are others using in the Mitchell O/D and Synchro transmission if GL-% Gear oil is bad for the brass synchros?

I talked to Steve and he says he has never had a problem using W85-140 GL-5 gears oil.
 
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