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OK, Mac & Patrick (oldgeezer)! Just so's y'all know I was at the computer all day typing up all the stuff I'm s'posed to know for the water chemistry part of my job. Didn't get to do even one li'l ol' experiment, so I ain't the one responsible for the 'shroom cloud.
The reason TCSTD and others, me included, don't like the motor oil in the tranny is because the gears will excessively shear the long chain molecules the oil is made of. That causes the viscosity to drop from the original 50 weight to below 30 rather quickly. The theory is that the actual gear oil retains its viscosity longer than the motor oil.
I will admit that I don't know whether this is true, but the circumstantial evidence indicates something bad is happening because many HD mechs are seeing tranny failures after the motor oil is used. I guess it's time to drop inon some oil experts and see if anybody has had an analysis run on the used motor oil vs. used gear oil after tranny use.
I have my own way of testing it out that cuts through all the advertising hype, I simply look at the magnet when I drain the trans and the absence of the metal on it sums it up pretty well in this guys head! Not scientific by any means, but it works for me.
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