6L80 Shift timing issues

[Balakayt.]

Alright I have a 2014 Silverado 1500 5.3 with a 6L80. About 2 years ago I tunned if using blue cat tool. I got the converter unlocked through 4th, changed the shift scheduling to where it drove great, it as like a brand new truck. The most important improvement I made was I got rid of the hard down shift from 3rd to 2nd when your coming to a stop. Before the tune it would jerk the truck each time and after the tune it was almost un noticeable. In the last couple years and about 40k miles I've made small adjustments but no major updates.

About 3 months ago I got the harsh closed throttle 3 -2 downshift again. In factory form that shift accurse at 14 mph. In my tune I had in there for years it happened at 7mph which softened the feel greatly. I have taken multiple logs and even tho the current tune asks for it to downshift at 7 mph it still downshifts at 12 mph. All other upshift and down shifts appear to be correct (fallowing the tune) as far as I can tell and it always says its in "normal" mode. I can not see anything in the logs that would cause this and im stuck at this point.

Could this be a physical issue/memory issue inside the TCM itself? I do have GDS and a vin subscription to reflash if needed but have not tried that yet.

Attached is the stock file the current tune and a Datta log. The first closed throttle down shift from 3 to 2 occurs at roughly 59 seconds.

Any input would be greatly appreciated.

2014 SILVERADO STOCK TUNE - Copy.hpt

Current trans trial shift pattern b.hpt

1 2 shift test.hpl

[ns158sl]

That log is 4 min and 7 seconds?

[Balakayt.]

Your right i was looking at the wrong time stamp. thanks

[mikez71]

Weird.. Your 2-1 downshift also occurs early.. (10 mph)

[Balakayt.]

I haven't tried setting shift pattern a (when in tow haul mode it shows pattern A on the scanner) to match normal yet. But its always in normal mode on the scanner so i don't have high hopes that will have any effect.

[mikez71]

Maybe ECM/TCM tire revs need to match?

tirerevs.png

[Balakayt.]

Is that screen shot from the "Current trans trial shift pattern b.hpt"? When I open it up this is what for the speedo calibration.

Screenshot 2025-06-09 185003.png

I think that screen shot you posted is from the Stock file. It is interesting that on the stock file they do not match. When I updated my tune originally for the larger tires i did make them match. That's was done before the trans was done tho so the whole time it was shifting great it would have been set like that.

[mikez71]

Is that screen shot from the "Current trans trial shift pattern b.hpt"? When I open it up this is what for the speedo calibration.

Screenshot 2025-06-09 185003.png

I think that screen shot you posted is from the Stock file. It is interesting that on the stock file they do not match. When I updated my tune originally for the larger tires i did make them match. That's was done before the trans was done tho so the whole time it was shifting great it would have been set like that.

Nevermind, that was the stock file. My stock file has the same differing values.

[Balakayt.]

Maybe i should try having an offset in my file? like the stock one.