Alright,

So here goes, I bought a 2000 Ford F350 CCSB 4X4 with 7.3 in September of 2023. The truck had 390k miles on it with a Motorcraft rebuilt engine installed and only about 27k miles on it (Previous owner had paperwork to prove). He told me the transmission was about 5 years old and was an "HD unit" but had no paperwork for it. The trans fluid was red and did not smell burnt but looked like normal, used trans fluid. On the test drive everything worked great, and I took it hunting the next month, towing my 8k lb (ish) travel trailer about 350 miles with a pretty steep climb up a forest service road to camp. Transmission got up to about 250 degrees in the Torque Pro app, but other than that everything went great, including the drive home (with the exception of having no deer with me).

This April (2024), I was towing my travel trailer mostly unloaded (6500 ish lbs) about 45 miles away and I got about 15 miles down the freeway, going about 65 when the O/D light started flashing. It seemed as though the truck went into limp mode. I pulled over, checked the trans fluid and it was still red with nothing leaking. I had forgot my obd scanner to read trans temp, so I sat for about 20 min to let it cool down and tried to go again. I couldn't get over 55 mph and then the O/D light started flashing again. I pulled over and it now had fluid leaking, not a lot, but a few drips coming off the pan. I assumed it was from the breather tube, likely from getting hot. I had the truck towed home and a buddy towed my trailer to camp for me. When I got home a couple days later, I ordered a OBD to USB cable and setup Forscan. I could see there were faults showing in both Shift solenoids A & B on the live feed data. Unfortunately, before hooking up Forscan I had removed the tow tune (superchips) and put it back to stock, which I believe cleared the DTC's from the PCM, so I was not able to get any Transmission related codes.

I did a full fluid flush with the directions from here, replaced the solenoid pack while I was in there and added the 6.0 trans cooler. This didn't fix anything. So, I dug into the harness. I found a couple wires with the insulation worn off, so I fixed those. I double checked that all of the wires related to the solenoid pack had good continuity and also checked continuity on all the speed sensors TSS, OSS and VSS (mine has all three). I also confirmed the range sensor was oriented properly. I reinstalled everything and still had faults showing for the two shift solenoids, even though they appeared to be functioning as they should, based on what gear I was in. I started thinking maybe I had a PCM issue, so I sent my PCM off to Diesel Tech of Chattanooga with all of these details. Great people to work with, but my PCM tested out fine and they checked it in one of their trucks and everything worked as it should. I then hooked up a pressure gauge and based on the service manual, everything appeared to be within spec.

So my game plan now is to replace all of my battery cables and grounds, to make sure the proper signals are getting to where they need to and also digging into all of the vacuum system and turbo system to make sure I have no leaks that could be throwing off any sensors.

I took a drive a couple days ago and screen recorded my data from Forscan, since my past cell phone videos likely caused some motion sickness. (4R100 shifting issue - Page 2 - Ford Truck Enthusiasts Forums). I noticed some TCC lockup issues (to me at least). I noted that in third gear, the TC doesn't lockup unless downshifting from 4th when I turn off O/D and even then, it doesn't show 100% lockup. In fourth gear, when the computer is commanding 100% lockup, I get anywhere from 0-40ish rpm of slip just cruising on the freeway. When I go to speed up, it would jump to about 120+rpm of TC slip even though it still showed 100% lockup commanded. Another odd thing I noticed was any time I tapped the brake pedal (just tapped not applied) the TC would unlock completely, I had thought there was supposed to be a slight delay in the TC unlock when brakes were applied. I've added the video below, which starts out with city driving (stop and go under 40mph) and freeway speeds start around the 13-minute point.

After this drive, I ran through all the self-tests in Forscan and still have no transmission related codes in the PCM. I think my torque converter is done for at this point and I am just looking to get some insight as to whether I am even on the right track here. Mark did provide some good and appreciated info on my previous posts, but any additional help is also greatly appreciated.

 

No in delay in lockup release for braking. If the brakes are engaged, even slightly, the TCC releases immediately.

 

Does anyone have an idea on what the acceptable amount of TC slip is for the 4r100, when its supposed to be 100% locked?

 

That depends on the calibration. Mine stays locked above about 40 mph.

 

Below 20 RPM slip is fully locked. There is some error in the speed reaings that can show up to 20 RPM when in reality it is fully locked.

 

So consistently above 20 RPM when commanded for 100% locked would indicate the torque converter going out?

 

It would indicate something is wrong. It might be the converter, it might be a seal in the trans, or a sticking TCC valve.

 

Following, what have you determined since October?

 

Im still working on figuring it out. I had some financial hurdles that put a stop to diagnosing..

I towed a skid steer (over 11k lbs) last weekend with it and watched live on forscan.. the torque converter was not happy.. slipping up to 130rpm when it was supposed to be 100% locked.. but it didnt overheat at all (35 degrees outside). And it had no flashing od light or codes afterward

Im still planning to replace all my battery cables and grounds and if that doesn't help, im going to look into the accumulator and valve body..

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So I took my truck to a mechanic who was looking into my transmission issues and he also could not find anything. He also looked into my shift solenoid faults and couldn't figure out why they would show a fault. He happened to get another 2000 F350 in while diagnosing mine and looked at the solenoid on that truck and it showed the same faults. He used to be pretty involved with the 7.3 tuning community and reached out to some other tuners and found that these faults were located in the hard code of many of the same build range as mine. There was nothing he could change in the pcm to correct the faults or to prevent the signal. So I'm kind of at a dead end again.

He did fix my Ebpv fault and I found a vacuum leak in the wastegate system that I fixed. I'm still thinking there is an issue with my torque converter locking and unlocking at random moments. I saw guzzles lockup mod and I am not very knowledgeable in that area and not very confident in building my own setup like that. Is there anyone that makes the lockup mod as a kit that would be willing to sell me one?

 

While driving to work today using forscan live, I saw the issue most predominantly between 50-60mph while getting up to freeway speed without significant throttle input (maybe 50-75% throttle) I watched the converter at 100% commanded lockup drop out of lockup for only about a second, anywhere from 40-75% lockup. Tcslip would jump and then it would go right back to 100% every 5ish seconds it would do this until I was able to get to a coasting speed of 65-70mph and it would stay at 100% lock.

To try to rule out the brake switch activating while bouncing, I held the brake pedal up with my left foot with no change.

 

Additional Update..

I got the Sonnax accumulator valves, springs and .472 line pressure modulator installed and all seemed well. It was shifting great until I put some miles on it and noticed 2-3 was not feeling good.

I finally got a flashing o/d light and it showed the p0782 code. Time for a rebuild!

Glad I finally have a reason it's been acting up and luckily everything ive done so far can be used on the rebuild.