6L80 locking out 6th gear above a certain output shaft speed.

Hello, I have found that a 6L80 I have locks out 6th gear when output shaft goes above a certain speed. Changing the final drive ratio in the calibration will affect when other shifts happen but this downshift happens at a certain output shaft speed every time, regardless of what I calibrate VSS to indicate. This is swapped into a car with very low gearing so the car is not going that fast when it decides to downshift from 6th gear regardless of throttle position, and even using the scan tool to hold 6th gear won't prevent this downshift.
I'd love to hear if anyone knows about this problem and has a solution. TCM OS is 24256125 and calibration 24256124

Baldur

Post tune and log

Here's the tune and a log showing what happens. Whenever VSS indicates 195km/h it drops 6th and won't go back into 6th until I slow down.

Would adjusting the tire size under the gear/tire wizard help any?

I tried changing the final drive ratio and everything so that the speeds reported by PCM and TCM would be closer to actual speed, that affected the upshift/downshift points but the speed at which 6th becomes unavailable remained unchanged, leading me to believe it is tied to output shaft speed in the TCM.

not fixed it ???

Hello my name is Egi
I live in Austria, Europe
I have the same problem with shifting from 5th to 6th gear.
My car is a Corvette C7 with 6 speed automatic and a changed differential to 3.42
if I come with the 5th gear at full load in the range of 5500 rpm and a speed of 245 km / h, the transmission does not shift into the 6th gear, whatever the driving modes

Just no help at all.....why?

Quote:

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Originally Posted by baldur

Here's the tune and a log showing what happens. Whenever VSS indicates 195km/h it drops 6th and won't go back into 6th until I slow down.

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where is the trigger? tcm?
can the tcm be cheated?

Has anyone play around with speedo hardware?
Because it seems to be a problem by VSS signal to/from TCM .
Speed output type can be : vehicle serial, vehicle repeat tos or wheel speed.

Does anyone have a fix to this? I'm experiencing the same problem with a customer who does standing mile.


I should add this is a 2012 CTS-V and at 6200rpm it's at 180mph.