I hate to burst your bubble, but you've been teaching wrong information. The radiator cooler
is a cooler, it NEVER heats the ATF
. Ever. In any condition.
put an air to oil cooler AFTER the radiator cooler
, NEVER put it before the radiator cooler.
I've measured ATF
temp in and out of the radiator cooler
along with the coolant temperature inside the radiator around the cooler in every operating condition I could come up with, and at ambient temperatures ranging from -40F to +115F. I never once came across a condition where the coolant around the transmission cooler was warmer than the ATF
. Not even close.
Now if the radiator cooler
were installed in the hot side of the radiator things would be different. Then the radiator would always heat the ATF
, even when the ATF
is already too hot. So that's why all transmission radiator coolers
are always mounted in the cold side of the radiator, where the coolant has already passed through the radiator and has been cooled.
Do you know what the coolant temp is in the radiator near the ATF cooler
when the ambient is -40F? Even after the engine warmed up and the engine thermostat opened the coolant on the cold side of the radiator never exceeded -30F. So how well will -30F coolant warm the trans?
To answer your question, what you are seeing is normal for a 4R100
. The 5R110 added a thermostat to the cooler line so that 90% of the normal flow bypasses both coolers
until the trans reaches 165F (nominal.) That's how to warm a trans up faster, just don't send fluid to be cooled when it's cold.