I just saw a video (
https://youtu.be/Fm8L7C9uE5I) that demonstrated how to fix an ATF leak on the 8-speed transmissions. the ATF heater and it’s incorporated thermal bypass valve is bolted to the side of the trans.
As I suspected there are two, approx 1.5” long o-ring sealed tubes, which looked to be about 5/8” in diameter that slip into the trans, and also into the back of the heater itself. The tubes easily are removed as they have an o-ring on each end. Engine coolant comes in to the top of the heater, and exits there, and the output and input connections to the ATF cooler are also on the top. The problem is how to couple the o-ringed tubes to some kind of connection to the ATF cooler lines, and completely remove/bypass the thermal bypass valve and ATF heater. As I’m sure this plumbing is all metric, sourcing the needed hardware would be “sporting”. A complicated operation needing some special fittings, and or a custom machined "manifold" that would accept the o-ringed tubes from the transmission, with drilled/tapped ports for the ATF lines going to the cooler. Clearly fabrication involved.
The two coolant lines could be simply connected to each other it appears.