The issue Im trying to solve is inconsistent 1>2 shift execution under WOT w/ gear selector in Drive (3rd).

1st gear holds fine, 2nd gear holds fine, all gears shift fine and feel good under normal cruising or part throttle, there are no DTCs, etc. From looking at my data, it appears to me that its not commanding the 1>2 shift according to the speed/rpms I have set in the calibration. I have not run into this issue before.. but as of today I made 8 WOT pulls through 1st to 2nd, and it failed to shift out of first on 6 of them. For the two times that it did shift out of 1st under WOT, the shift was firm and scratched the tires… felt really really good. The application is a C10 w/ a turboed 6L @12 psi boost, with a freshly built 4L80E (Jakes stage 2 kit w/ 500 miles on it) and Gen3 ECU tuned w/ HP Tuners. I have been tuning for the past few months, working my way up in boost pressure, and just today came across this issue for the first time. I have looked at the calibration and the recordings/logs from today, though I don’t see a whole lot of transmission parameters to choose from, and I have been unable to determine what my issue is.

The parameter that I have been looking at to determine if the PCM is commanding the shift to 2nd gear is [TransCurrentGear]. My assumption is that this is the “Commanded” Gear??? Meaning, when this changes from 1 to 2, it means that the PCM has commanded the 2nd gear shift to start??? What Im seeing is that this stays at 1 all throughout 1st gear until hitting the rev limiter, though I have my tables to shift at 5900 RPM and 61 mph setpoints. If this speed seems high to you, it is because I have 3.08 gears and a stock (tight) converter. I have verified my [Vehicle Speed] is correct and matches a GPS.



I have attached my tune, as well as three recording. A summary of the recordings is as follows:


- 1to2ShiftSuccessful_1Jul

*1 to 2 Shift is successful however occurred later than normal (around 6200) when normally it takes place (around 6000)


- 1to2ShiftUnsuccessful_1Jul

* 1 to 2 Shift is unsuccessful. As you can see, the [TransCurrentGear] remains at 1 until hitting rev limiter at 6400 rpm


- 1to2ShiftUnsuccessful_2_1Jul

*1 to 2 Shirt is unsuccessful. Something unique about this recording is that if you watch the [TransCurrentGear] it bounces back and forth from 1 to 2 and right away back to 1 prior to hitting the rev limiter.



I did some forum searches and most of what I returned was mechanical. This smells more of a software/calibration issue to me, as the thing shifts great and on time when not in WOT, and if it does actually shift to 2nd under WOT, the shift feels short/firm. And as mentioned before, 2nd gear holds great at WOT, once its actually in 2nd gear.



Im at a loss of what to try next, or if there is additional parameters that I need to be looking at to figure out the issues. Any and all help would be greatly appreciated.

 

I'll have to look at these over lunch when I get to a computer with HPT...but in the meantime, is this a 2500 tune? Or is it a segment swapped tune?
Do you have tire size and gearing properly calibrated for?

 

The ECU was out of a 2002 truck w/ a 4L60E, so yes I did do a segment swap for the 4L80E. Yes the gearing and tire size are calibrated property, as the speed in HPTuners matches the ground speed on my GPS (+/- 1 mph). Thanks for your help!

 

so the stock computer gets kinda funky with WOT shifts when you tell it to ignore MAF readings (like when you force OLSD mode)

google up "Bluecat Trans tool" and unify the WOT RPM/MPH shift tables. you may have to skew higher than your target shift point to get the actual

 

It requires both spoed and rpm to be satisfied to shift. Bump your speed down and try getting it to shift by rpm. Since you have a stock tight converter, start soft. If you want it to shift at 6600 rpm, set it for 6200 and creep up on it, see how that works. Also, make sure your speed sensor is reading correctly and consistently in hp tuners. I'll try to look at your log when I am on a PC.