TCC solenoid lockup stuck off when hot and max towing

[Toadman]

Have a 2007.5 2500 HD Duramax Allison with 250k kms and EFI Live 5 DSP, with DPF and EGR delete. Tows 12,000 lbs with additional weight in the box (heavy toyhauler with ATV on deck and lots of fuel/weight in truck box.), 23,000 lbs combined. Yes, over recommended weights. Typically only run Stock (1) Economy (2) or Tow (3) settings. Often play with Tow/Haul switch on hilly terrain to maximize fuel economy and lower RPM while not lugging the engine.

Problem: When engine (100*) and environment (28*C) is hot and towing heavy up a large hill the TCC solenoid lockup gets stuck OFF (P0741). Upon complete cool-down normal transmission operation resumes. This has happened twice, first time engine temp rose quickly to an overheat condition that was immediately cooled down. Second time temp was only slightly over normal cruzing operation.

Have dropped the pan, inspected wiring, changed internal and external filters/fluid and tested/verified (but ONLY at room temp) the TCC solenoid resistance of 5.2 ohms. No metal, minor clutch material visible in pan.

Question: Does EFI LIVE have any history of TCC lockup issues for the Allison when heavy towing and hot operating conditions?
Transmission gears work flawlessly, Torque Converter clutch "could" be going or the solenoid could have high temp issues.

Only have access to basic ODB2 code reader, not a graphing scan tool to check TCC lockup slip. Mechanic directed to ask this question, knowing that EFI Live was installed on the truck.

Thanks in advance for any advise or input.

[S Phinney]

Unless the tranny was tuned as well it is working off all stock data. The ecm is tuned by EFI Live and that doesn't change the tranny parameters. I usually tune both myself.

Sent from my SM-G920V using Tapatalk

[joecar]

You need to check the TCC lock/unlock tables to make sure they are not upside-down or otherwise conflicting.

[Toadman]

Thanks for the replies, after a fluid and filter(s) change, wiring inspection and solenoid cleaning by hand the problem has not yet returned. I have stopped switching the Tow/Haul button and let the computer handle the shifts and not push the engine as hard on the hills. At first glance it even appears that fuel mileage has improved from 30 down to 24 L/100km even with higher engine RPMs much of the time. Time will tell if this problem returns. Hoping as long as the engine and tranny temp are keep below 115* and 100* respectfully on big hills that the issue will not arise again.