I have a automatic in a 01 7.3 and it has about 40k on a rebuilt trans. The other day I was driving down the road and it started surging, the rpms stayed the same but the truck would lunge forward and then nothing then lunge forward and sounded like the motor would quieten down then roar, rattle, up then quieten down during this. I kept driving and it seemed to correct itself. Last night i was pulling a big horse trailer and 5 horses and it started doing the surging or whatever real bad, i took overdrive off and it corrected the problem almost completely. Any ideas guys??? torque converter? Transmission? motor? lol im lost as last years easter eggs.. Thanks for any opinions!