My Dad has 95 dually automatic with 375k+ on the clock. He says while driving down the road if he hits a good enough bump, the merger of road to an overpass lets say, the truck will seem to shift out and back into overdrive quickly. Rpms will jump from 1500 to 2000 for a second or so and then fall right back.

It does it sometimes while driving empty, more common when pulling a trailer.

Could this this be a lose wire or the transmission slipping?

Ya'lls insight is appreciated.

 

my vote would be a wire probably a ground

 

My truck started doing the same thing, turned out to be a combo of low fluid, a dented oil pan on the drivers side, and a dirty filter. I fixed all three at once so not sure if I could pin point it to one thing. Mine would also slip out when taking hard left turns.

 

or the brake pedal, one flicker of the brake lights will do that