I have a 1992 gen 1 Cummins diesel and the over drive has been acting up for some time now. It goes in and out of overdrive at will and going down the freeway one minute at 70 MPH and then down to 55MPH will get me shot. I changed out the TPS unit twice but a $500 I must look for another solution. I read a lot about TPS problems and OD shifting problems on different Diesel Forms on the internet and got a lot of great information that inspired this fix: I picked up a 5,000 ohm (linear taper) potentiometer (for $1.50) at radio shack. I disconnected the TPS plug and clipped it off and striped back the insolation to expose the braided wires. I purchased 10 feet of black electrical braided 3-strand wire. Like what you might use for and extension cord and using heat shrink and solder I connected the new wire to the TPS wire from the harness. It does not matter which wires are connected you will figure that out later. Just solder the wires and cover the connection with the heat shrink. Then rout the cable back along the existing wiring harness and over to the firewall and snake it in with the other existing wires. I installed the potentiometer in the dash near the OD button. You will have to play with the connection until you get it right by testing the potentiometer as you drive down the road. It is not hard you only have two wires to deal with. When you find the right combination solder the leads to the potentiometer and be sure to install the heat shrink. Now I can "dial-in" the shift point of my OD. It works great! I can cause the OD to shift (and down-shift) at a constant speed anywhere from about 33 to 50 mph. I have had this fix installed for over a year and it is SUPER COOL!