ATF vs. Gear Oil In Man Trans - Revived

mduralia

Registered User
Guys,

I have a very good friend who is the best mechanical engineer I've ever known. This guy knows so much stuff. I asked him about using gear oil rather than ATF in the man trans. He suggested 85% volume of ATF and 15% volume 75W-140?

What do you guys think?
 
Mike, here's his message to me...

This is what the Mech Engr. sent me:


If it were me I would do the following:
6.3 pints is 100 ounces. I would get pure synthetic ATF transmission fluid. Measure out 85 ounce's of the pure synthetic ATF and add 15 ounce's of Mopar part #04874469 synthetic gear and axle lubricant 75W 140. Sounds high but it pours better than the non-synthetic. Flows great and has high volume of EP additives.

My thoughts regarding this are as follows:

The lower viscosity is there for flow and fluid shear efficiency.
The gear shifting is better because the viscosity is slightly improved and the lubrication film isn't breaking down.
The Mopar is what is put in and required if you are going to tow. This is typically used in the differential. Get it at the Jeep dealer. Take care of it because it is $22/qt. I had to purchase 3 quarts for my jeep. The noise disappeared and the differential has run substantially cooler.

I suggest the pure synthetic because it will not break down at all. It also has improved extreme pressure additives to keep the gears from rubbing. Like, that is what we want to do. The end viscosity has to be low enough to allow for free flow of the lubricant in the transmission.

I would start with 15% and see what happens. If all the clashing doesn't go away, drain out 5 ounces and put 5 more of the 75W 140 to replace it. I don't think you will have to do this though.
 
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