Made a PTO cover for the getrag out of 1/4" thick Lexan. I read that it can take 240* for long periods of time, and 285* for short periods. I am now reading about people getting their transmissions up over 240* and even to 260*! if I fill the trans up with 5 quarts of fluid will it stay cooler? Thanks!

 

Yes, it'll run cooler. How much cooler, I don't know without testing.

The reason it will run cooler is that the amount of heat created by driving will not change with a given input of power and load (like 2% grade @ 5000#). When you had additional fluid, you are increasing the heat absorbing materials - therefore every quart of oil has to absorb less heat because there is more oil overall.

Another way this will increase cooling is because you'll have a greater surface area the oil (goes farther up the tranny case) is trying to disappate the heat. More surface of the tranny case exposed to fluid, the better the case will heat up and transfer that heat to the exposed air.