I bought a 1996 f250 with the 4x4 7.3l power stroke. I bought the truck knowing it didn’t want to shift from first to second gear unless you let off the throttle. I have recently started to try and diagnose the issue. I started off by buying a Bluetooth odb2 code reader and using forscan to pull any codes. I do not get any codes when reading the pcm nor do I have a check engine light and the od light on the shift column is not blinking. The main problems I am having are as follows when I first drive the truck after disconnecting the batteries it will shift fine at first (it usually shifts fine through all the gears once or twice). Then the rpm’s to get it to shift out of first will begin to increase to the point that I have to bring it up to 2500 rpm to get it to shift out of 1st. I originally thought it was shifting into second but I used the obd2 scanner and found it was going from 1st straight to 3rd. Then once it’s in 3rd if I get to 2k rpm it will shift into 4th every single time causing the engine to bog way down. I have cleaned the vss sensor in the rear axel, the speedometer bounced slightly when I first got the truck so I sent it out to get repaired. I have continuity from the solenoid pack back to the pcm, I replaced the fluid and filter and since I had the pan removed I removed the valve bodies cleaned them and made sure all the springs were not broken and the valves moved freely. the 3rd brake light was blown when I bought the truck but I have since replaced it. I have check resistance on the mlps as well and it within tolerance. I even sent the pcm to diesel technology of Chattanooga to have them test it and it came back fine. I’m not sure what else to do any help would be greatly appreciated.

 

Get Forscan free at www.forscan.org. With this you can log data and we can figure out what's wrong.

What is the PCM seeing for vehicle speed? Is the PCM commanding the shifts and they are not happening, or is it not commanding the shifts? What is TP (throttle position) doing?

 

I am currently using forscan. When watching the pcm it is commanding the gears, as far as I can tell when showing speed it seems to be correct. The throttle position when trying to monitor the voltage from the obd2 port it doesn’t show any change. I removed the position sensor and tested the resistance and I believe it works correctly? But I can always check that again. I was thinking maybe I have an issue with a wire going back to the pcm since it doesn’t show any change in voltage on forscan, but I still have throttle response so I’m just a little confused by that