Coming back from La. this past weekend towing the TT @ about 55mph I lost power, truck would maintain 55mph but no more for about 8 seconds then I would get power back for about 10 seconds, loss power for about 8 seconds, and this went on until I reached 68 mph, cruised fine at 70 mph. Also noticed below 55 mph if it lost power it would decrease in speed until it downshifted, I would have full power with OD off.

 

I might be jumping to conclusions but, It is an electrical problem with your truck. Not a major one (hopefully). It has to do with the ground in the computer. There are a number of fixes to it. But there is not one true answer. Look on the "common problems and how to do" thread Rodda has posted some good info. For me I took out some quick disconects that were on my passenger side battery. That did the trick for me. There is also a recent thread that the guy that had low fluid in his battery. He had the same problem that you had a cupple of years ago and had a relapse of the same problem.

Well good luck with it and i hope it is helpfull.

 

I had the batteries and cables changed out about 2 months ago. I will look around at all the wiring.