At what point does torq converter engage?

[CPLTECH]

Could a tech tell us how the TC is designed to operate under various conditions?

To me it seems too willing to unlatch with the slightest pressure from the gas pedal. I note that lock-up occurs ~45-50MPH when up to engine temp and in 5th gear. Yet, so easy to unlock. When towing in 4th, again too easy to unlock. I guess I was used to my 98 Tahoe in which a mech tweaked the computer program to hold the TC in lock-up slightly longer than orig and change final shift speed about 5 mph sooner. Been told you want it to unlock to save clutch wear(?) but at the same time massive heat is generated which also signifies poor MPG. What’s the happy sweet spot? Is there some aftermarket programmer or chip available to address this concern? Also on this subject, are there times the TC is in partial lock-up?

I notice that the “Bully Dog” product will tune the engine of a Nissan but not our transmission (but does on other brands).