Aristides
Transmission fluid has a broad working range. However the optimal working temperature is usually 175 to 220 degrees. The greatest heat is in the torque converter, with recorded temperatures (trucks pulling loads) in excess of 350 degrees.
Sergey
An additional clarification to my prior post.
Normal operating temperature of an engine is approximately 190 to 200 degrees. The proper radiator cooling system maintains that temperature range via the thermostats.
To maintain this operating temperature range, most engines are designed to run with coolant temperatures between 160 and 200 degrees.
Transmission fluid heats up more rapidly under load as opposed to being in park. It’s theoretically possible for a vehicle idling in park, (or driving slowly) for the radiator coolant temperature to reach operating temperature (160 to 200 degrees) before the transmission fluid reaches 160 degrees. In such a scenario the radiator cooler would actually head the fluid instead of cooling it.
Would this damage the transmission? No. it’s still within its operating range of 175 to 220 degrees. This hypnotical example only reaffirms that the external transmission cooler should be after the radiator cooler if the objective is to return the transmission fluid in its coldest.
Apologize for the long post
really appreciated