Truck: F-550, 6.0, only 30k miles.

Problem: Missed 3-5 shifts, seemed to drop to 'neutral' at random.

Codes showed:

P0767 Shift Solenoid D Electrical.
P0766 Shift Solenoid D Performance / Stuck Off.

I replaced the solenoid with a new factory solenoid, replaced filters, fluid flush with fresh ford sp fluid. (Stock solenoid was available locally, and needed the truck up and running or I'd have waited to get a modified gogo solenoid from Empire.) ***The old solenoid tested fine, so I used it to fix a friends truck that was having the same problem.***

Problem remained - so replaced wiring harness inside transmission, and seemed to have the problem fixed.

Started the same problem again - less than 500 miles since replacing the harness.

I have more time now - so I'm going to go ahead and swap in the modified gogo solenoid and take the opportunity to verify the electrical connections on the internal harness, as well as add a redundant grounding strap to the transmission case itself to alleviate other potential problems. (This should also have the transmissions ready for more power, since this truck is about to get the EGR 'fixed', head studs and tuning - which is why I don't mind 'double checking' my work.)

Beyond that - the only thing I can think of is to start troubleshooting the wiring harness on the truck. The connector at the transmission looked perfect, with no scorched pins or obvious loose connections to suggest a problem. (used a digital camera to check for arc-scorched pins)

Is there another common place to find problems in the wiring harness, or am I going to have to break out my wiring diagrams and trace this harness all the way through the truck checking for faults on that circuit?

(tried the search function - without much luck, but it's possible I missed something.)

Thanks in advance for any advice you guys can offer.

 

I would wait for Mark K to weigh in (he almost always does on 5R110 threads) before I did anything else AFA buying parts goes. You may just be throwing away money that you don't need to.

 

You want to also check the wiring from the trans to the PCM. Check the wires for continuity, short to power, and short to ground.

 

Thanks Mark. :-) I'm doing that now - took a short break to check here in case anyone had input. Disassembled the plug that goes in to the side of the transmission to check for properly crimped pins (and get test leads on them), and I've just started hunting for the matching wires up by the PCM.

Doing my best to be patient. I'd be thrilled if it was as simple as running 1 new wire or adding solder to a badly crimped connector.

 

Update - crimped pin connectors look good, continuity is good, shows no fault to power or ground.

Best I can think to do now is reassemble everything with dialectric grease, and borrow the PCM out of a friend's 6.0 to see if the problem persists.

The only thing I haven't figured out is where the small ground lines from the solenoids (yellow/white) are connected to the single larger (yellow/white).

 

The grounds from the solenoids do not connect together. They each run separately to the PCM. The grounds are where the PCM controls the solenoids. The solenoids have +12V power any time the key is on.

 

Thanks for correcting me, that makes more sense. (Saved me spending time hunting through the manual chasing an incorrect assumption)

After disassembling the connectors at both ends (which all looked clean) and reassembling packed with dialectric grease, truck seems to be running well. I'll repost if anything changes.

 

Hey T8R. Is your truck running good after cleaning and putting dielectric grease in? If not, what fixed your issue. I'm having trans issues as well p0710 and p0713. Thank you. -Steve