This may seem to be **** about this but in the past I have always used the largest external trans cooler that could be fitted in conjunction with the factory cooler in the radiator. The logic was to cool the fluid from the trans before it inters the radiator cooler at which time would bring the fluid temp back to proper operating temp. I have never had issues with transmissions over heating but am I being over critical of the fluid temperature?

 

Thats IMO actually kinda backwards to the norm. I would preferr the cooler to be after the radiator myself . I like to see trans temps as cool as possible within reason. ABOVE FREEZING in other words.

 

Though it is nice to have 2 coolers, the radiator cooler will only allow the fluid to be as cool and engine coolant and it would depend on how you have it routed.

If I ever go back to a trans like an auto I will do just a external rated at least 24,000 GVW. as long as the fluid is above freezing temps, your fine.

 

I run an external cooler only, and my normal pan temps are 145-150*.