Attention: TDR Forum Junkies 
OK, I got this from another member that did it to his second Gen truck. I have now done it on my 93 and I like the way it works. I just got back from a 2000 mile trip towing the travel trailer and it worked great. I use the OD button a lot to turn the OD on or off manually and that probably is part of the reason I like the way it works.
The member I got this from did not post this because he was tired of some folks slamming any new ideas and he didn't want the hassle. I will say that if you want to use this, I hope it works as good for you as it did fo me. If you don't want to use it then that's OK also. Just leave it be!
You need to get the following:
1)A 5K potentiometer, 1 watt rated. It should have three terminals on the back. I used a one turn pot, you can use a 10 turn if you want finer control.
2)6'-8' of 3 conductor 18 gauge shielded wire. The colors are red, black, and white. Don't use solid wire as it will tend to break easier. I couldn't find any of this so I used a red, black, and green 18 gauge automotive wire and made up a harness. The green was substituted for the white.
I mounted the pot in a small project box and secured this to the dash just to the right of the cargo light switch but you can put it any place you can get it to fit.
Run the wires from the TPS up to the dash. Cut the wires off the TPS leaving a few inches on the sensor. I used insulated push together connectors and on the end of the TPS installed the opposite type that were installed on the TPS wires. This allows the TPS to be easily reconnected should the need ever arise.
The Red wire will connect to the violet with white stripe, the white to the orange with dark blue stripe, and black to black. the violet is the 5V going to the TPS, the orange is the voltage that is leaving the TPS and the black is the ground.
Connect the white to the center connector on the pot and the black and red to the end connectors. If the pot works backwards, reverse the red and black leads. The black should be on the #1 connector and the red on the #3 if the leads are numbered on the pot you have. Seal the connections with dielectric grease to prevent corrosion.
After hooking up, set the voltage out of the pot to about 1 volt. On the pot I used, all the way off was at the 7 o'clock position and full on was at the 5 o'clock position. Setting the dial at 9 o'clock gave me one volt. That caused the transmission to shift at about 35 MPH with normal driving. Pulling the trailer it was a little early and after playing around, I am now set at the 12 noon position and the transmission shifts at 45 MPH. This is good when pulling the trailer.
I noticed that the transmission downshift can be felt much better and there is a little more engine braking this way. All in all, I am pleased with the set up. It never once gave a problem with not shifting or shifting out of OD when going down the road if not at the set point. The heavier the throttle, the higher the shiftpoint. one drawback is the transmission doesn't shift out of OD when passing and you ned to manually take it out of OD if this is desired or needed to pass.
I taped the sensor into a wiring harness and also removed the mount from the top of the pump. Now it is easy to get into the top end of the pump for adjustments.
I have probably left out something but this is the general idea. It will work guys! If you don't understand something or if I left out something, ask me.
The member I got this from did not post this because he was tired of some folks slamming any new ideas and he didn't want the hassle. I will say that if you want to use this, I hope it works as good for you as it did fo me. If you don't want to use it then that's OK also. Just leave it be!
You need to get the following:
1)A 5K potentiometer, 1 watt rated. It should have three terminals on the back. I used a one turn pot, you can use a 10 turn if you want finer control.
2)6'-8' of 3 conductor 18 gauge shielded wire. The colors are red, black, and white. Don't use solid wire as it will tend to break easier. I couldn't find any of this so I used a red, black, and green 18 gauge automotive wire and made up a harness. The green was substituted for the white.
I mounted the pot in a small project box and secured this to the dash just to the right of the cargo light switch but you can put it any place you can get it to fit.
Run the wires from the TPS up to the dash. Cut the wires off the TPS leaving a few inches on the sensor. I used insulated push together connectors and on the end of the TPS installed the opposite type that were installed on the TPS wires. This allows the TPS to be easily reconnected should the need ever arise.
The Red wire will connect to the violet with white stripe, the white to the orange with dark blue stripe, and black to black. the violet is the 5V going to the TPS, the orange is the voltage that is leaving the TPS and the black is the ground.
Connect the white to the center connector on the pot and the black and red to the end connectors. If the pot works backwards, reverse the red and black leads. The black should be on the #1 connector and the red on the #3 if the leads are numbered on the pot you have. Seal the connections with dielectric grease to prevent corrosion.
After hooking up, set the voltage out of the pot to about 1 volt. On the pot I used, all the way off was at the 7 o'clock position and full on was at the 5 o'clock position. Setting the dial at 9 o'clock gave me one volt. That caused the transmission to shift at about 35 MPH with normal driving. Pulling the trailer it was a little early and after playing around, I am now set at the 12 noon position and the transmission shifts at 45 MPH. This is good when pulling the trailer.
I noticed that the transmission downshift can be felt much better and there is a little more engine braking this way. All in all, I am pleased with the set up. It never once gave a problem with not shifting or shifting out of OD when going down the road if not at the set point. The heavier the throttle, the higher the shiftpoint. one drawback is the transmission doesn't shift out of OD when passing and you ned to manually take it out of OD if this is desired or needed to pass.
I taped the sensor into a wiring harness and also removed the mount from the top of the pump. Now it is easy to get into the top end of the pump for adjustments.
I have probably left out something but this is the general idea. It will work guys!
If you don't understand something or if I left out something, ask me.
Oo. 
Still searching for that gremlin. 
