ok so my dads truck is sputtering around the 1700-1800rpm range and we thought it had something to do with the motor but it ONLY happens in overdrive. when we hit the tow/haul it dont do it anymore... any help?

 

I would guess the lockup clutch TOW/HAUL mode increases line pressure. If the converter clutch is failing where it may chatter at normal lower pressure it may hold at higher line, Also the PWM strategy is changed some what also which could point to a clogged PWM solenoid or a worn bore for the converter regulator valve.
But I would say its trans/converter related. How many miles on the truck/trans?

 

bout 140 on both