Generic Transmission question.
Something bugging me is what chart or setting adjusts the up-shift on the transmission based on how fast you press the accelerator pedal. In other words. If I am say accelerating and progressively press the pedal slowly up to about 75% or so it will not shift. However if I were to let up on the pedal and do a rapid pedal movement I will get an upshift to get the vehicle moving. What gives this rate of pedal position vs shift timing?
It's based on the Part throttle Shift table. It shifts the shift mph higher as the throttle is increased.Originally Posted by TheMechanic
So it is responsible for the shift based on the rate of increased throttle? Because I can slowly get to about 75% without an upshift if it is a gradual slow increase but something as slight as a rapid 15-25% will give me an instant upshift
I would blame that on an entirely different setting. I would be very interested to see a log of this with a good channel list scanning. As mentioned before, if you ramp the throttle in (either fast, or slow) the ECM/TCM should instantly start looking at the newest/latest TPS as a signal for the next upshift. AFTER a set MPH and RPM are met. IF you are experiencing an immediate or close to that upshift after giving MORE throttle, that is opposite the normal way of things
Last edited by village_idiot; 08-25-2021 at 04:50 AM.
No totally normal response to pedal "Speed". GM Dealer tech for over 2 decades. Literally every vehicle from 2000's and above do this. Just wondering what parameter or table if it is even changeable. Cruising along in 3rd gear if i gently/slowly press the gas pedal it will not shift to 2nd until I get way into the throttle maybe 75%. If say I am at 1/4 throttle and stab it a little to say under 1/2 throttle it will shift immediately to 2nd gear. The shift correlates to the speed at which the pedal is pressed. Somewhere that has to be a parameter that changes this rate. I know that on GM vehicles it is reduced significantly when cruise control is engaged to reduce what GM call "Shift busyness" so when you go up and down gradual grades your trans does not shift it will hold a gear.
The Mechanic ... if you are referring to the older P01 and P59 PCMs - there are many shift parameters not available (not defined) in HP Tuners.
These include:
- Kickdown (downshift) tables based on TPS position and vehicle speed.
- Vehicle speed thresholds for various shift strategies.
- Vehicle acceleration thresholds for various shift strategies.
There are no doubt more related parameters in the OEM calibration - which I am not aware of - that may contribute to the phenomena that you are describing.
Ahh, I had some terms confused there I think. I thought you were describing that if you quickly gave it more pedal, it would shift UP as in, cruising in 3rd, stab pedal and instantly shifts up to 4th. I was all like but wait, it doesnt work like that?! Lol
Yes exactly what I was looking for. Not specific to P01's and P59's. Just about everything seems to do it. Makes sense that it is not in the HPT software. Maybe it should be as it would be nice to accentuate these.
village_idiot
Oh and there goes my dyslexia again. Upshift 1-2-3-4 ect downshift 6-5-4-3-2-1. Sorry about that.
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