I need to increase transmission longevity in our fleet vehicles. We're seeing failures between 100 and 175k miles for transmissions that should last far longer. I am convinced the problem is related to, or aggravated by, TCC slip as failure seems to begin in the converter. A local transmission shop I work with agrees and they believe the mileage on our fleet vehicles at time of failure lines up with the odometer readings on trucks they work on.

There is an hptuners thread that recommends setting TCC regulator offset to 90 psi and TCC regulator gain to 1.5 for full lock on aftermarket converters. I can confirm this will force TCC appy in third through sixth gear shortly after upshift/downshift and will keep TCC locked well enough so TCC Slip is zero or negative (silly TCM math). This has the effect of keeping TCC locked until sufficient throttle pedal angle is reached to trigger a downshift. The 6.0 has enough power to drive the vehicle with TCC locked, but I am hoping to release TCC before downshift occurs to see how that affects driveability and economy.

Does anyone have any recommendations for good reading about TCC control strategy including TCC Regulator Offset and TCC Regulator gain? I'd be especially interested in GM training material that mentions these values.

Edit: I have a copy of a calibration released by GM for "reduced TCC failure." It has a differennt cal ID but any parameters that are different between the original cal and this one are not part of the tuning software I use.

Thanks,