Well, I didn't make that chart, but TCI transmissions has it on their site as well.
The tranny doesn't need help getting warm. It does that just fine. The thing about the radiator's built-in cooler is that it is fluid-fluid, not fluid-air. Put on a pair of soaking wet oven mits and you'll see how much more efficient fluid-fluid is over the dry mit fluid-air in transfering the heat from a casserole to your hands.
It's important to keep the cooling system in your truck up in order to also keep the tranny cool. But the tranny WILL get hotter than the engine and the engine's cooling system won't adjust for it enough so the factory puts an auxillary cooler on.
I do not think that particular lubricant needs to be hot to function. It's also used in hydraulic systems that don't deal with anything like the power that a transmission in a vehicle does. It's in my Bobcat--the mechanical clutches are bathed in it and a little 3gph pump drives a 1,200psi 2-valve system--and trust me, the lines do not get hot--the pump gets warm and it definately needs lubrication--which the fluid at maybe 120*F (the pump body gets much less warm than our waterheaters output) provides. But if the fluid is used to lube+cool something like an automatic tranny that might have a 200hp load slipping 5% in it, that is 10 hp worth of pure waste heat transfered to the fluid and it will easily boil, break down into deposits, harden and destroy seals and lose it's viscosity wiping out clutches and bands.
I will definately agree that you cannot overcool and automatic tranny.
This is from amsoils site. According to them (and they know nothing about it, i'm certain) you should definately shoot for that 175*F.
