VEGASROBBI

IM using the stock T42 tune from a 2007 Silverado 4wd LH6 E38. Upshifts are great. Also, when I come to a stop it clunks and drops into 1st, so the downshifts are delayed. There is no kickdown 4-3, 3-2 or 2-1.

I tried to lower the downshift mph tables with EFI Live-no effect.

Thanks Robbie.

performabuilt

iTrader: (25)

Suggest checking the TPS for proper function .

VEGASROBBI

Interesting, in the PID's the T42 only validates "Accelerator Effective Position" and reads 0% at 0 throttle (ETC of coarse).

On the other hand the E 38 only validates "Absolute Throttle Position" and never reads below 20%, even KOEO.

I checked the signals from the APP and they appear to be within range and no Synch APP sensor codes exist.

Is this normal? BTW Thanks for the fast reply.

performabuilt

iTrader: (25)

Unfortunately as I have stated before I am not a tuner, However I do know the TPS can be bad and not set a code as long as its within its functional range. and that kickdown is very dependent on the TPS signal

joecar

Questions:
- does the scantool show the correct vehicle speed...?
- does the scantool show the correct throttle position...?
- is each downshift table at least 5 mph below the corresponding upshift table...?

The trans controller may be trying to use a different TP than what the engine controller is sending it... I don't know how you would configure/match them up other than finding engine/trans controllers/calibrations that were originally paired together.

tptransmission

On t42 controllers the transmission uses effective pedal position for its shift points so if it continually reads 0 you have a controls issue.

VEGASROBBI

Questions:
- does the scantool show the correct vehicle speed...?
- does the scantool show the correct throttle position...?
- is each downshift table at least 5 mph below the corresponding upshift table...?

Yes the scantool reads VSS correctly in both the ECM and TCM, I checked with GPS.

I don't know if the TP is correct. In the scantool the TCM and ECM read different values. The ECM never reads below 20%.

The trans controller may be trying to use a different TP than what the engine controller is sending it... I don't know how you would configure/match them up other than finding engine/trans controllers/calibrations that were originally paired together

The T42, E38, LH6, 4L65e and thier calibrations are all from the same vehicle.


Joecar I read your informative Trans Tuning Guide, and no, there does not appear to be a 5mph difference in upshift vs. downshift; but this was the stock tune?

tptransmission the TP value is not always 0, it starts at 0 unlike the ECM

tptransmission

That is normally the signal the transmission uses for shift pattern. The ecm has a few parameters for throttle such as blade angle etc. it may never show zero depending on which one it is.

VEGASROBBI

Thanks for the replies. I believe the kickdown and downshifts were inhibited because my ECM had a 4WD tune and was not recieving a valid 4 lo signal. I went to a 2WD tune and all is working.
Were working on getting a valid 4 lo signal to the E38 so we can run the 4WD tune, Thanks Robbie.