Need Help with T43 6L90 OEM Shift

[gaduser]

Included are two OEM tables from my 2011 CTS-V: the Part Throttle Shift and the Normal TCC tables.

I constructed the third table in trying to understand how the system works.

"Lock - Upshift" contains subtracted speeds. For example, at 0 Throttle, 4th locks at 37 MPH, after the 3-4 shift at 27 MPH. The subtracted MPH is +10 indicating that Lock occurs 10 MPH above the Upshift. The positive 10 makes sense.
However, at 50% Throttle, 4th locks at 37 MPH, after the 3-4 shift at 68 MPH. The subtracted MPH is -31 MPH. That seems to show that Lock occurs at a much lower speed than the Upshift, clearly not possible.

Similar logic applies to the Release - Downshift calculated results.

It seems to me that the transmission and/or TCM may Release the Converter on every shift, be it up or down. In that case, many of the table entries may have no effect because they are below an upshift MPH or below a downshift MPH. If that is the case, I wonder why those are in the table at all.

I will appreciate any and all help toward my understanding of this. Actually, I wonder if I made a stupid error in my reasoning. If so, let me know.

I could experiment with the car to learn more. However, that seems like a really bad idea because I don't believe that I know what I am doing, yet.

Thanks much!
207552075620757

[Tre-Cool]

The logic behind the TCC is pretty simple in my mind.

The in-gear lock speed could technically be the same speed across the whole gear. so if it's lower then the oncoming gear \ up shift it's irrelevant. It just means that it should lock as soon as it hits the gear. As the speed requirement for lockup has already been met.

Now Unlock you generally want it to be;

1) Lower then the lock speed, so you can maintain lock even while coasting. Until the trans either down shifts or you get to an rpm where it's better for the trans to slip (on the converter) so as not to lug the motor at a low rpm. I'm not a fan of lugging motors are low rpm so I set my tables to either down shift or let go of TCC lockup.

2) Higher then the lock speed can you used if you want the converter to unlock at a high pedal level before or in place of a downshift. Obviously the rpm you get is going to be entirely different based on either stock or aftermarket converters.

[gaduser]

Tre-Cool,

Thanks for the response.!

In this OEM tune, the 4th gear lock speed is 37 MPH at all throttle settings. The 4 to 5 upshift, at 50 % throttle, is at 86 MPH.
Do I understand that the converter is locked before, during, and after that shift?
Would that not cause a very hard shift because the engine RPM is much higher than required to run at that same 86 MPH in 5th?
With stock diff. and tire size, 86 MPH, in 4th is at about 4000 engine RPMs. In 5th, with the converter locked, at 4000 RPM the speed would be about 116 MPH.

That is why I suspect that the converter always unlocks when the transmission shifts. The only other thing that comes to mind is that the clutches, in the transmission, slip during the upshift while the RPMs throttle down.

Clearly, I still don't yet understand how the system functions.

Thanks again for your reply! Further comment and criticism is welcome.

[Tre-Cool]

the unlocking on shifting is another parameter entirely that can be set. so if your locked in 3rd the converter will momentarily unlock, then re-engage again in the stock calibration. it can be changed however.

[gaduser]

the unlocking on shifting is another parameter entirely that can be set. so if your locked in 3rd the converter will momentarily unlock, then re-engage again in the stock calibration. it can be changed however.

Thanks again.

I did make a quick pass through the V7.5 Tune Tool without finding a way to turn that "auto release/lock" function on and off. I will look again.

Some time ago, I considered buying the SW to compile and disassemble the code for this MCU family. However, the prices convinced me that unless I was in the business, it was too expensive. If I had those tools, I would probably spend way too much time at this hobby.

[joecar]

The GM calibrations generally always unlock the TCC across any shift... EFILive may not show the parameter for this.

[gaduser]

joecar,

Thanks for the info - makes sense.

gad