the problem is getting worse, when the truck is cruising with no load you let off the pedal and coasting then give it just a touch of throttle it lopes real bad (whap,whap,whap,whap) then as the truck slows down and it puts load back it goes away. I tried to make it do it in park with just light idle but it wont do it, just at a cruising speed, it never has dont this before. any ideas. I dont think it is trans or converter, its kinda like when you deck the motor and let off it kinda lopes for a sec, then levels out???