97 F-350 Dually RWD with 460 and e4od (Yes it's a 97 but still has EEV-IV)
Shifts way early, take off from a stop and it immediately shifts into high.

Everything works great to shift it manually including the overdrive button. OD Light isn't flashing, CEL is not on.

For a long time this was intermittent, it would work great for days then one day shift odd then go back to working fine.

After reviewing several forums and threads until i went crosseyed from reading I started out checking the small things and moved on to larger.

So far i have:
- Tested throttle position to be in spec
- tested the gear selector switch to be in spec and adjusted properly
- Tested the speed sensor to be in spec and the speedometer isn't jumpy or anything (it only has the speed sensor on the rear diff)
- Cleaned the connectors on the cluster (I read about the speed signal being sent to the cluster before it goes to the PCM)
- Replaced solenoid pack wiring harness plug at the transmission end. (The bare wires were exposed and connector corroded quite a bit inside.
- Cleaned the pins on the solenoid pack which were also in pretty bad shape
- Replaced solenoid pack
- Checked PCM for leaky caps/corrosion. No sign of any issues visually

No matter what I do, it just does the same thing. Everything that has worked for others to fix the same thing have not worked.

Any thoughts?

 

4wd? Sounds like the computer thinks it is in 4wd LO.

 

RWD

It's acting almost like the C6 would if the throttle cable to the transmission was out of adjustment like it doesn't know what to do

 

Check engine light isn’t on but do you have fault codes? From the thread (E4OD Shifts waaaaaaay early) about shifting too fast.

 

Check for codes: www.troublecodes.net/ford

 

The only codes showing are 622 and 633 Sorry forgot to mention that in my original post.

 

633 is your problem

 

How am I getting that on a 2wd?

 

A short in your harness. The computer is the same 2wd versus 4wd.

 

Could I just clip that wire off the pcm? Looking at the diagram it also goes to the 4x4 Low Light on the dash and is grounded when its in 4 low

 

The wiring for the 4wd dash indicators may or may not be present in the under dash harness.

I think it would be wise to find the damage to the harness.

 

That was explained in the screenshot I put in post #4.

Type “code 633” in the search in the upper right corner. There are several threads about the issue and start reading. A few of the threads have wiring schematics that you can use to find the bad wire.

 

Anybody have any specific locations that they've found bad wiring?

So far not finding anything

Any previous threads I've found so far guy just says it's fixed but doesn't share what the issue was

 

Progress Update:

Pulled cluster to verify the wiring to the 4x4 low light. Those pins on the cluster conector are not even populated so I can rule that out. But according to the diagram shouldn't there be a +12v source going through the 4x4 light and into the pcm? Looks like it should be high 12v when "4x4 is off" and pulled to ground when "4x4 is on". Without those wires being populated where does the pcm get the 12v signal from to tell it that 4x4 is off?

Pulled the entire transmission wiring harness out from the junction under the brake master. Laid it all out, unwrapped it completely, inspected it, and metered out every pin from one end to the other including the gear selector connector, transfer case conector, transmission connector, and 02 sensor connector. So at least that section of harness I know is 100%

Here's the weird part. The Light Blue/Black wire from the transfer case connector (which is just capped off on the frame rail) changes to a different color wire (Looks like black or something dark) at the connector under the brake master. It does match what's going to pin12 at the pcm, however from that connector to the pcm I have no continuity... So maybe that indicates something broken in the big main harness?

Driving me mad but at least I've ruled out a bunch of stuff.

 

Further update:

The wires coming from the transfer case connector are just terminated in the main harness and go nowhere.

Pin 12 from the pcm just goes down a bit in the harness and is terminated and goes nowhere.

Pin 12 has no short to ground

PCM Harness has no shorts

All signs point to 'replace pcm' also backed up by the ford manual for code 633 if no wiring issues replace pcm :/ I just wish this wasn't a weird one that they want $1000 for a used one :O