LMM nearing end of warranty

[Mark Rinker]

Running great, not overly worried about warranty denial. Installed first performance tune (+80hp setting) using my Predator. Nice power and reasonable unloaded mileage - 19mpg observed, much of it in 4HI on icy road conditions at ~60mph.

Q: Who has the best LMM tow/economy tune out there, while maintaining stock EGR and exhaust equipment?

[Mark Rinker]

Okay, so far so good with this tune. Had the rare occasion to drive the truck unloaded for some distances, and 19mph isn't hard to maintain with a light foot and speeds under 65mph.

However, under heavy acceleration, there are HUGE pauses (de-fueling?) between upshifts...you almost have to lift to get the shift complete and back into acceleration mode.

No codes thrown, and it doesn't feel like the tranny is slipping...so what to do? Will unhooking the batteries and letting the TCM relearn help?

[DmaxMaverick]

If you tow heavy a lot, it takes a while for the tranny learn to catch up with empty. Heavier/longer, takes longer to un-adapt after you unhook. If it smooths out empty, you may notice a similar condition when you hook up again. The more you drive it empty, the more driving it will take to relearn with a load on.

[EdHale]

Interesting question Mark. My LBZ is bone stock, but I do go several months between moving my 5'er with lots of unloaded driving during this period. Would resetting the TCM make the first few miles of towing again better? Will unhooking both batteries do it? How long to leave unhooked.

[DmaxMaverick]

If the adaptive learn is reset, the first few miles will be less accurate, and then will improve over time/miles. It starts from a default baseline, and adapts from there. Later models seem to be a bit less profound in transition compared to earlier, but I think Mark's use is probably at the extreme edge of the TCM's learning curve. Meaning, his conditions aren't typical, and may present a different TCM learn process than a weekend'er. Later models, I've heard (not verified), can actually store several different driving styles and conditions, and require a lot less driving to recognize and adapt to a stored set of parameters. Earlier models (2005 and earlier) have only the to modes (T/H on/off), and adapts to each change every time.

The adaptive learn is in persistent memory, which requires a tool command to reset it. Some DTC errors will force a learn reset, but something has to go wrong before that happens.

[Mark Rinker]

Thanks...I'll reset it properly tomorrow at my buddies repair shop.