Torque converter will lock and unlock rapidly

2000 Ram 2500 A/T with light mods, no tranny mods.

Between 30 and 40mph if I give my truck around 10-40% throttle it will start jerking and slipping as the torque converter keeps locking and unlocking. I've been letting my family drive it lately with specific instructions on how to care for the transmission (No overdrive in town is at the top of my list) and I'm thinking they've just been giving it hell.

Anyway, the tranny gets to around 150 degrees on a 70-80 degree day which is around right, a little warmer than normal I thought but nothing to write home about. The fluid on the dipstick looks and smells good, however there are a few bubbles on it when I go to pull it out. Also, I'm going to double check but I believe it MIGHT be leaking from a tranny cooler line. If it IS leaking from a tranny cooler line, could air in the system cause these symptoms?

Thanks!