Harsh shifts mechanical or electrical

[marine5811]

96 F350 4x4 CCLB E4OD 7.3

I have been having a harsh shift issue lately. It started suddenly about 2 weeks ago. My 1-2, 2-3, and 3-4 shifts are jarring but my TC lockup is silky smooth.
(One thing should be noted. Until today I have had a broken gear shift lever handle and no OD button or OD OFF light, so no flashing "OFF" could be observed.)
The only things that changed before the harsh shifts began: I had a gooseneck installed at a trailer shop. Welding was done and my batteries were disconnected and reconnected. I picked it up and was on the freeway within 1/2 mile. (Could being WOT on the freeway while the PCM was relearning its adaptive strategies affect line pressure baselines?) Did not experience harsh shifts for the entire drive home. (The harsh shifts had not begun yet.) The next day I drove the truck about 1/4 mile then executed a forced downshift at 30 mph from "D" to "2". Downshift was normal. Immediately after reselecting "D" and accelerating from the stop, my 1-2 shift almost knocked my teeth out. Transmission has been shifting harshly every day since then.
I have been pouring over the service manual and a bundle of E4OD files I have accumulated. It was starting to look like accumulator/valve body issues until I decided to keep it simple at first and disconnect the batteries for a few minutes and reconnect them to reset the PCM. I did it and went for a short drive. All of my shifts were perfectly smooth. They stayed smooth until today. I got my new gear shift lever in today from Ford and installed it. My first 1-2 shift after completing the installation was harsh, as were all the others, however TC lockup is still smooth.

Now my two questions:
1: Can I assume that my problem is electrical and not mechanical? After disconnecting my batteries, my problem went away for almost 4 days. If it were a mechanical problem (internal to the trans) there would be no way for the problem to go away, correct?
2: Can anyone tell me which sensors the PCM looks at when determining trans control? I know the VSS is looked at as well as the MLPS.

RockyardJo is going to spend some time giving me a scan with his copy of Auto Enginuity tomorrow. I'll post the results and maybe somebody can help translate. Thanks guys and gals.

[POWERSMOKIN]

the ICP also has a role in determining shift firmness. If mine is unplugged, it feels like it will twist the driveshaft.

How does the fluid smell?

Did you disconnect the batteries again after installing the shift lever?

How old is the tranny?

[marine5811]

Fluid smells great.
I did dis/reconnect the batteries again after installing the shift lever. I'm 1300 miles later (after reconnecting batteries) and still no problems or harsh shifts. I haven't updated this thread because I'm still not 100% sure what fixed it (or if it's even really fixed). I'm not a big advocate of saying "...this is what was wrong with my truck and this fixed it..." It always irritates me when guys suggest solutions with no proof, evidence, or real reason why it works. I'm trying to figure out the issue and solution.
As for the transmission, it's the original (250000 mi) but it has been very well maintained other than being a dedicated tower.

[POWERSMOKIN]

250k on the original tranny?! WOW!

But yeah i hear ya, only if its a definitive fix. But you never know, these electrical systems are stupid. Pulling the wires to replace the shift lever could put it in a limp mode or something...

[marine5811]

Hey all. Just stumbled across this thread and remembered to wrap it all up.

The shift problem was a P1728: Transmission slip error.

This threw the truck into limp mode which I couldn't observe because my shifter end and OD on/off light were broken off.

Since, I have replaced the shifter and installed an Aeroforce Interceptor. The OD light was flashing and the Interceptor retrieved the P1728 code for me. Cleared the code with the Interceptor and all's well that ends well.

[eldridge201]

Originally Posted by marine5811

Hey all. Just stumbled across this thread and remembered to wrap it all up.

The shift problem was a P1728: Transmission slip error.

This through the truck into limp mode which I couldn't observe because my shifter end and OD on/off light were broken off.

Since, I have replaced the shifter and installed an Aeroforce Interceptor. The OD light was flashing and the Interceptor retrieved the P1728 code for me. Cleared the code with the Interceptor and all's well that ends well.

Thanks for coming back and letting us know what fixed it. Still running well at 250+? Man, that's somethin'. Especially for a tranny and one that towes.

:beer :

[marine5811]

Well it's running ok, I suppose. Rebuild in the near future.