68RFE P0731 problem 2018 RAM 2500

[McGyverBob]

Hey everyone, thanks for looking.
I've been doing a lot of research last month and a half regarding this problem but I haven't found a solution yet.
I hope some of you can chime-in with some thoughts...

Transmission was rebuilt 2 years 7 months ago, approx 35k miles ago.

Components installed:
ATS valve body billet channel plate/separator plate/accumulator pistons & plate kit
ATS Co-Pilot piggyback transmission management computer
Smart-Tech Overdrive Clutch Housing/drum Kit
RevMax coated transmission pump plate
RevMax Zero flex billet pump body
RevMax high performance 700 rebuilt kit
RevMax solenoid pack
TransGo shift kit
ATS thermal bypass
DPC dual disc low stall converter.

Tuning:
SCT BDX tuner, boxed "Performance" tune. No custom tuning has been done.

The current problem started suddenly one day, a few weeks ago, after I disconnected the negative battery ring terminal for the ATS Co-Pilot harness in order to connect another ground ring terminal for a horn I was installing. I did not remove the main negative battery clamp/cables.

Once the transmission gets hot (issue slightly noticeable around 125 degrees and gets worse the hotter it gets and pretty bad once trans temp is up to 180 degrees….
1st gear slip and slam when beginning to accelerate from a red light and throws code P0731: Gear 1 Incorrect Ratio.
Hard shifting, up and down.
If I BABY it from a dead stop then I can avoid the slip, slam and the code.
Occasionally, there is a delay from park to drive or into reverse but hasn’t happened much since the problem started, perhaps four times over the last month and a half with this issue.
Also, when on highway at 60 mph or more and the engine load at 1% to 9% (but not with foot completely off accelerator pedal and coasting), I can feel the trans cause two “braking” actions within a second followed by two or three seconds of normal, then it repeats. Kinda like as if I were to quickly but gently tap my brake pedal twice within a second, leave it alone for two seconds then continue to repeat the pattern. Torque converter engagement/disengagment??

The issue is not present 100% of the time but more like 95% of the time.

I can tell if the problem is “ON” because I can hear the trans make a sound reminiscent of a worn ball bearing while at a red light or in park/neutral.
When the problem is “OFF”, that noise is not present.
When the trans is hot I can hear that noise come and go but with no specific pattern of time. When the trans is cold, less than 115 degrees, it doesn't make the noise. Torque converter??


I have tried:

Performed a quick relearn, no change.
Replaced transmission input speed sensors, no change.

Dropped the valve body and visually inspected it, checked that the bolts were not loose and torqued to spec, I replaced the three seals for Low/Reverse clutch, 2nd clutch and 4th clutch, installed new flat and spin-on filter, and refilled with new Mopar transmission fluid… no change.
Then I replaced the transmission output speed sensor and the problem seemed to have gone away but then returned a couple days later after regular in-city daily driving (maybe I didn't let the transmission get all the way hot and that's why I didn’t notice it again for a couple of days??).

I removed the SCT boxed “performance” tune, restore factory tune and removed Co-Pilot AND harness, then performed another quick relearn and it slams into drive from park and the moment I barely touch the accelerator pedal it goes into limp mode 4th gear only, super hard park to drive shift and hard 1st to 4th shift and throws these codes:
P0721, output shaft speed sensor range/performance
P0716, input shaft speed sensor range/performance
P1794, speed sensor ground error
Way worse than when ATS Co-Pilot is in place so it's like the ATS Co-Pilot is doing a better job of managing the trans but the Co-Pilot is not in control 100% of the time, it modifies signals to the trans when I deems necessary.

I reseated all plugs (MAP, accel pedal position sensor, line pressure sensor, output speed sensor and 23-way solenoid pack connector)... no change.

Looking for help I called and talked to a couple of guys at ATS Diesel. They suggested the possibility of the solenoid pack having gone bad. That thought crossed my mind too so I bought another RevMax solenoid pack, removed the valve body once more to swap it and put everything back together, reconnected the ATS Co-Pilot device and harness, reapplied the SCT boxed “performance” tune, cleared DTC’s and went for a long drive… the problem is still there; the slip and slam and P0731: Gear 1 Incorrect Ratio.

While on that long drive I used the SCT tuner to monitor the line pressure and I noticed on a few occasions the main line pressure on the trans went up to around 178 psi, so I’m thinking the pump is functioning fine.

?? I’m not sure where to go with this. Bad converter?? Bad TCM?? Valve body issue with the ATS separator plate cross leaking??

When the trans is cold it shifts smoothly and through all gears normally and there is no slip and slam when beginning to accelerate from a stop. Trans gets up to about 100 degrees and I can start feeling the hard shifts. Once at 120 degrees or so then the slip and slam can start to happen and gets worse and happens more frequently as the trans temp goes up to 180 degrees.

Thanks again for looking,

Robert
2018 Ram 2500 Laramie, 6.7 Cummins, 68RFE Transmission, ATS exhaust manifold, Bank Monster Ram intake, high flow air intake, SCT BDX tuner, 5" lift, 37" tires

 

[Ritchie_Rich]

With a modified truck there’s no telling. Take it back to the rebuilder.

 

[Burla]

Did you already take off thermo bypass, I see yes good? And you mean this happens at 125f and gets worse as it goes up? When you rebuilt it you did solenoid pack? I see you did revmax, did you save OEM solenoid or toss it?

Does it do the same thing when you are in tow haul mode? Sounds like a possible VB/solenoid or tcm issue or sensors that operate it but you should see codes. Since everything else is newish, how many miles on old sensors? Dang I see you did that already too, good job. dunno man, sorry just brainstorming.

and its not going into limp?

 

[RamLife1500]

That’s a brutal one, but a few things really jump out reading this.

1) Converter or converter clutch issue
The “double braking” feeling at light throttle highway speeds sounds like TCC hunting or partial lock/unlock, and the bearing-type noise that comes and goes when hot also leans converter. A failing stator sprag or TCC piston can act totally normal cold, then go sideways once the fluid thins out. That can absolutely trigger ratio codes in 1st when the PCM sees mismatch between ISS/OSS.

2) Internal cross-leak that only shows up hot.
Even with billet parts, separator plates and upgraded accumulators can still cross-leak once everything expands.

The fact that pressure hits ~178 psi doesn’t mean the clutch is actually holding.

3) Ground / signal integrity issue.
Those speed-sensor and ground codes (P1794 especially) plus the timing of when this started makes me suspicious of a shared ground problem. If I were you I would-

-Ohm-check grounds from battery → block → trans case hot and cold
-Load-test grounds (not just continuity)
-Inspect the 23-pin connector pins for heat-related spread

4) Less likely but possible: TCM. To check this-
-Line pressure + clutch apply pressure test hot (not just commanded pressure)
-Swap in a known-good converter if possible before pulling the whole unit

The noise + TCC behavior is what keeps pulling me back to the converter, especially since everything else has been touched twice already.

Not a fun spot to be in, but I don’t think you’re crazy—and I don’t think it’s tuning alone either.

 

[wsh56]

What Trans. do you have?

 

[wsh56]

They make a tune for trains now. I've heard after having your engine tuned, sometimes the transmission will "learn" a different shift pattern.

 

[wsh56]

"a tune for trannys"

 

[Sherman Bird]

Hey everyone, thanks for looking.
I've been doing a lot of research last month and a half regarding this problem but I haven't found a solution yet.
I hope some of you can chime-in with some thoughts...

Transmission was rebuilt 2 years 7 months ago, approx 35k miles ago.

Components installed:
ATS valve body billet channel plate/separator plate/accumulator pistons & plate kit
ATS Co-Pilot piggyback transmission management computer
Smart-Tech Overdrive Clutch Housing/drum Kit
RevMax coated transmission pump plate
RevMax Zero flex billet pump body
RevMax high performance 700 rebuilt kit
RevMax solenoid pack
TransGo shift kit
ATS thermal bypass
DPC dual disc low stall converter.

Tuning:
SCT BDX tuner, boxed "Performance" tune. No custom tuning has been done.

The current problem started suddenly one day, a few weeks ago, after I disconnected the negative battery ring terminal for the ATS Co-Pilot harness in order to connect another ground ring terminal for a horn I was installing. I did not remove the main negative battery clamp/cables.

Once the transmission gets hot (issue slightly noticeable around 125 degrees and gets worse the hotter it gets and pretty bad once trans temp is up to 180 degrees….
1st gear slip and slam when beginning to accelerate from a red light and throws code P0731: Gear 1 Incorrect Ratio.
Hard shifting, up and down.
If I BABY it from a dead stop then I can avoid the slip, slam and the code.
Occasionally, there is a delay from park to drive or into reverse but hasn’t happened much since the problem started, perhaps four times over the last month and a half with this issue.
Also, when on highway at 60 mph or more and the engine load at 1% to 9% (but not with foot completely off accelerator pedal and coasting), I can feel the trans cause two “braking” actions within a second followed by two or three seconds of normal, then it repeats. Kinda like as if I were to quickly but gently tap my brake pedal twice within a second, leave it alone for two seconds then continue to repeat the pattern. Torque converter engagement/disengagment??

The issue is not present 100% of the time but more like 95% of the time.

I can tell if the problem is “ON” because I can hear the trans make a sound reminiscent of a worn ball bearing while at a red light or in park/neutral.
When the problem is “OFF”, that noise is not present.
When the trans is hot I can hear that noise come and go but with no specific pattern of time. When the trans is cold, less than 115 degrees, it doesn't make the noise. Torque converter??


I have tried:

Performed a quick relearn, no change.
Replaced transmission input speed sensors, no change.

Dropped the valve body and visually inspected it, checked that the bolts were not loose and torqued to spec, I replaced the three seals for Low/Reverse clutch, 2nd clutch and 4th clutch, installed new flat and spin-on filter, and refilled with new Mopar transmission fluid… no change.
Then I replaced the transmission output speed sensor and the problem seemed to have gone away but then returned a couple days later after regular in-city daily driving (maybe I didn't let the transmission get all the way hot and that's why I didn’t notice it again for a couple of days??).

I removed the SCT boxed “performance” tune, restore factory tune and removed Co-Pilot AND harness, then performed another quick relearn and it slams into drive from park and the moment I barely touch the accelerator pedal it goes into limp mode 4th gear only, super hard park to drive shift and hard 1st to 4th shift and throws these codes:
P0721, output shaft speed sensor range/performance
P0716, input shaft speed sensor range/performance
P1794, speed sensor ground error
Way worse than when ATS Co-Pilot is in place so it's like the ATS Co-Pilot is doing a better job of managing the trans but the Co-Pilot is not in control 100% of the time, it modifies signals to the trans when I deems necessary.

I reseated all plugs (MAP, accel pedal position sensor, line pressure sensor, output speed sensor and 23-way solenoid pack connector)... no change.

Looking for help I called and talked to a couple of guys at ATS Diesel. They suggested the possibility of the solenoid pack having gone bad. That thought crossed my mind too so I bought another RevMax solenoid pack, removed the valve body once more to swap it and put everything back together, reconnected the ATS Co-Pilot device and harness, reapplied the SCT boxed “performance” tune, cleared DTC’s and went for a long drive… the problem is still there; the slip and slam and P0731: Gear 1 Incorrect Ratio.

While on that long drive I used the SCT tuner to monitor the line pressure and I noticed on a few occasions the main line pressure on the trans went up to around 178 psi, so I’m thinking the pump is functioning fine.

?? I’m not sure where to go with this. Bad converter?? Bad TCM?? Valve body issue with the ATS separator plate cross leaking??

When the trans is cold it shifts smoothly and through all gears normally and there is no slip and slam when beginning to accelerate from a stop. Trans gets up to about 100 degrees and I can start feeling the hard shifts. Once at 120 degrees or so then the slip and slam can start to happen and gets worse and happens more frequently as the trans temp goes up to 180 degrees.

Thanks again for looking,

Robert
2018 Ram 2500 Laramie, 6.7 Cummins, 68RFE Transmission, ATS exhaust manifold, Bank Monster Ram intake, high flow air intake, SCT BDX tuner, 5" lift, 37" tires

Install a genuine FACTORY filter. NOT an aftermarket POS. P0731 stand-alone screams oil starvation. Especially when you describe a pump cavitation noise.
All you have to lose is some fluid and a filter,