Hey everyone! First timer and hoping I can get some help or know if I'm on the right track. I recently bought a new to me 1997 F-250. When I bought it, the truck was having some taking off troubles. As if I was towing some heavy heavy loads. After getting up to around 20 MPH I would be able to cruise just fine and everything seem to shift just fine. I came to discover that a bunch of wires to the PCM was smashed as if someone put a gallon jug on the PCM harness. I got all the wires repaired and now I have power but I have erratic shifting. It feels like it tries to shift early and then actually shifts shortly after. Most of the wires that were repaired was almost everything transmission related (thank you to a former post to find the PCM Diagram). One of the wires was repaired was the VSS to the PCM. I changed the trans fluid and put a new filter in after it was repaired in hopes that would help the erratic shifting but it didn't. I also took the VSS off and wiped it off. I couldn't see any metal shavings either when I did this but still have the same issue going on. I was wondering what you all thought? Maybe replacing the VSS? Maybe the transmission is going out because of all wires lost controlling the shift solenoids and toque converter and for who knows how long? I don't have cruise control but I do have OD and no ABS light. I also have no check engine light so no codes either. I know reading older posts the VSS will make the speedometer bounce everywhere but mine isn't doing that either. Thank you for reading!

 

If it's not the wiring.
All tail lights working with non LED lights?
Exhaust back pressure valve opening? That can make it feel like it drags.
EBP tube near alt clogged up? Can make for odd shifts.

 

Thank you for the response! All lights work, nothing is out. Do you by chance know how I can check if the valve is stuck open?

 

Are you assuming no codes because no check engine light? Most transmission codes will not turn on the check engine light. If you want to fix this you MUST read the codes.

 

Oh no, I used the free forscan and torque app to check codes and both said there wasn't anything

 

Use Forscan to monitor data. Does it show vehicle speed as steady or erratic?

 

I have not done that yet but I will definitely do it and relay the data. Thank you for the help! Also, I'm sure you get this a lot but thank you as well for the write up on changing the transmission fluid. I read it and was able to drain the torque converter because of it so thank you for that as well!

 

Psom is another possibilty. Does the OD light on the shifter ever flash? Does that light work? It is the signal for transmission codes.
We have a 92 that is doing something similar. On it, i know it is the PSOM because we have a 95 that we swapped it with after eliminating everything else.. The 92 drives perfect with the other PSOM installed. The PSOM processes the VSS sensor readings on the way to the Transmission Computer (TECA). The TECA controls the shifting.

The PSOM for the 92 was sent for rebuild, came back, worked one day perfectly, and then quit working right again. It is now on its way back to be checked again. I am thinking we may be ahead to just have the odometer programmed correctly for the 92 and be done with it but we will see what happens this time.

 

Hey everyone! Sorry for not getting back. It's canning season and when I was going out to get some numbers off I had some bad idling problems and could hear grinding. My water pump was shot so I've been replacing that but I will follow up again once I get it back up and going. Thank you all again for the help! I appreciate it

Carltonwebb. No flashing OD no ABS light nothing like that. I have no codes either when I've connected it to a scanner but I will do what Mark suggested here soon once I get all the coolant flushed out and get her back up and going

 

X2 on the PSOM. My erratic shifting was corrected with a rebuilt one. I did have a VSS code, but a new VSS did not correct the issue. Something to consider if you can’t find any other solution.