[Dead Parrot]

What temp thermostat is in the motor? The trans cooler is on the cold end of the radiator and if the water entering the hot side is fairly cool due to a lower temp thermostat, it might not be much above ambient when it gets to the trans cooler.

As others have said, if the trans is otherwise working normally, don't worry about the cooler temps. Many folks spend a lot of money on aftermarket finned pans and stand alone coolers trying to lower their transmission temps.