Jerry,

I think its going to depend on how the converter clutch is wired.
On my 69 C10 you can almost see the trans temp climb if you don't get it up into overdrive while towing. Its because the converter clutch is wired to only lock up in OD. I also have the vacuum switch to unlock the converter at low manifold vacuum (84 chevy p/u style). That causes the trans to heat up quickly if the engine load gets high, even in OD.

regards,
Leon