My father inlaw has a 99 1 ton dually, cummins 5 speed, lately when your cruisin at highway speeds, out of the blue you just start losin power, and it doesn't matter what you do with the gas pedal it makes no diffrence, but if you down shift and get the rpm up it starts to pull again, and you can re enter 5th,, and the problem goes away, it could be fine from 5 minites to a week


any idea's, thanks Skippie

Check your fuel pressure. You may have a bad lift pump and or injection pump. Try cycling the key on/off 3 times and see if any codes pop up on the odometer.

Make certain the lift pump is working, if it is change the fuel filter(shouldn't be but 10-12 bucks at autozone or advance).