I've finished putting some pressure switches as well as a manual switch for my 47RH TC lockup and I have been driving this 12k# motorhome with TC locked up quite a bit. I have it setup so that it locks on at 44 mph and turns off when boost is above 8 psi or when the speed goes under 25 mph (I wish it's 35mph though).

I must say the rpm drop is worth it. However, i'm curious about the side effects of driving with a transmission with the torque converter locked, especially in a heavy vehicle like mine. The engine seems not to care, but how about the transmission?

 

As long as you don't slip the converter clutch or the internal clutches & bands in the trans it should run cooler with the converter locked.

 

I smoke out everyone within a quarter-mile radius with a 14mm pump and 6x16 injectors if I use lockup too much....other than that I see no downside.