What is the transmission thermal bypass?

Well, on most vehicles in the past, the the route that the oil takes.

It goes from the transmission through the cooler and then back to the transmission.

So in more recent vehicles, the manufacturers have installed a device that's a thermal bypass.

And what it does is when the vehicle's cold, the oil will enter the block and then exit the block.

It won't let the fluid go to the cooler.

And then as the drivetrain heats up there's a valve inside that will open and allow the coolant or the transmission fluid to go up to the cooler.

And let's see, John wants to know, how do you determine the optimal balance between coolant flow rate and heat exchanger efficiency when designing high performance cooling systems?