Speedometer and power drops

When I hit a bump the speedometer will drop and even though the engine runs smoothly the power drops for a second before coming back and the speedometer goes up again.
The cruise control does not work. That seems to have something to do with it. I figured it was a loose wire somewhere so I would stop every now and then along the road and send my teenage boys out to just push together whatever wires they could see and that worked for a couple years. A mechanic happened to visit a few years ago and I remember him saying it looked like the wire had hit something underneath and the wires were pulled slightly from the plug. He fixed it borrowing a soldering gun. It worked fine for the last four years but we have lived by the ocean the past several years and I figure that that has now corroded those same wires again, but I do not know what they were. The boys are grown and gone and do not remember and the mechanic is also gone.