4L60E Line Pressure Adapting

[RobertISaar]

so how does this work with no input shaft speed sensor? upshift(and downshift) adapts, i can see, since engine speed can be measured and tracked, but how is steady-state adapting done? the torque converter slip(both intentional/stall and clutch slip) makes using engine speed problematic, especially if the converter clutch isn't locked.

[EagleMark]

Internal calculations for engine torque. MAF and VE have to be correct for the calculations to be accurate.
PID GM.TRQENG


The pressure control solenoid (or force motor) is controlled by the PCM by varying the current flow to the solenoid.
The PCM can vary the current from 0.0 amps (high pressure) to 1.1 amps (low pressure).
The pressure control solenoid produces a "torque signal pressure" which determines the final transmission line pressure.


Pressure Control Solenoid Pressure can be logged with PID GM.TFMPRS It will increase as engine torque increases and also spike before and during TCC Lock up.

For a tuned shift kit instead of hard parts install...

Setting Shift Times to 0.000 disables Adapt Learn for shifts so you can dial them in with increasing Base Pressure for each shift. About 25% is all that should be added on stock trans.

Then if that is not enough reducing Torque Reduction in up-shifts will. Again about 25% is safe on stock trans. If you watch your spark advance during logging you will see a small blip loss of spark advance when this is happening. That is if all other Torque Management has been removed/disabled.

If you go to far? The nice firm shift turns into a BANG and it pretty rough on hard parts of trans and drivetrain. But until that point all you do is reduce slip/wear and heat in trans.

I've got my stock trans shifting nicer then a couple shift kits I've driven without spending money and installing a kit. At WOT I know chirp a tire in 1>2 shift.

Still trying to figure out exactly what Adaptive Learn is learning too? Seems that info is not in any bin definition? Has to learn to something? At this point my logs in testing are pointing back to actual logged shift time GM.SHIFT12, GM.Shift23, GM.SHIFT34 and there errors?

[RobertISaar]

adaptive learning = the PCM changing line pressure from its base calibration. used for both shift time/feel control and steady-state to stop clutch slippage.

without an input speed sensor, i don't see how steady-state can be done unless estimated based on the learned values from upshift adapts?

[EagleMark]

From everything I've read, learned and data logged I don't think engine RPM and or speed has anything to do with it. It's all a PCM calculation off of Delivered Engine Torque.

Abuse seems to use speed and RPM. But Torque Management and Torque Reduction for shift points does not.

[RobertISaar]

that would imply that it's an open loop situation then.... that's kind of scary for anything other than a bone-stock engine if not dialed in perfectly or having the torque calculation set to overcalculate to give a safety margin.

[buddrow]

Im not an expert but in the adaptive learning process, the computer uses engine speed(rpm) drop when the shift is commanded to determine the fill time of the clutch pack thereby "learning" the " clearance of the clutch pack" and adjusting line pressure to speed up or slow down the clutch/band apply. The pcm stores this info, and over many many drive cycles usually, learns how u drive and adjust the shifts accordingly. Hope this helps and if I my info is erroneous feel free to post corrections.

[RobertISaar]

from what i can tell, that has to be how it learns adapts... it uses the calibration as a starting point and uses upshift adapt data for steady-state correction. i'm not a fan of that at all.... you either have to have the calibration perfect or overcompensate in it to make sure that there is enough line pressure at all times.

wonder if anyone has added an ISS to a 4L60E?

[RobertISaar]

seems GM eventually made a 4L70E.... and it has an ISS.

now to find an application list.....

[buddrow]

Indeed GM did introduce an ISS in the "4L60E" in 2004 but there is no rhyme or reason as to which trucks got one. Its a hit or miss situation.

[RobertISaar]

strange.... anyways, i was gathering this info for my 7730 TCM project... i guess i'll have to impliment an option for non-ISS transmissions to use upshift adapts as a basis for steady-state modification.

[billygraves]

Robert,
What are you asking about? Can the Transmission Adapt Upshift Pressures in the 4L60-E? Shift pressures can be "Adapted" in some L60 applications and only under the right conditions. The algorithm is called "Modeled Ratio" It is loosely based on a sudo Input speed and calibration tables that have slip across the converter in the table. So the pressures can be adapted based on this very complex routine. That is about all I can say without getting into so much detail that it is just to much to type.

[RobertISaar]

upshift adapts, i can understand how they're done since shift progress can be tracked via engine RPM drop(when they quit dropping or at least quit dropping so quickly, shift is complete, compare tracked shift time with desired shift time, etc, etc).

but without an input shaft speed sensor, i was curious how line pressure would be adjusted to prevent any clutch slippage when not shifting. any slip in the torque converter would throw off being able to use engine speed compared to output shaft speed(with a known gear ratio to multiply with).

when i was doing my own disassembly of $A1, i found that input shaft speed was calculated/estimated there for torque management purposes. i never checked to see how reasonable the estimates were, but with a ~2100 stall converter, i don't know what kind of results to have expected.

from the sounds of it...... assumed converter slip is input into at least one calibration table to create the pseudo-ISS RPM value.

[greggbruceauto]

when I went to 4l60e school when I worked at the dealer, they said it uses engine rpm, and has a "window" for the time it takes to complete a shift from the time it commands the solenoid to change state, to when the rpm finishes dropping, and it knows if the converter is locked up or not, and I'm assuming it has calculated slip based on the output speed/what gear it is in vs. engine rpm.

IF the engine temp is correct, and the trans temp is correct, and it is within a certain throttle position (wot is NOT an acceptable learning area) and speed, then the computer will modify the line pressure to compensate for a too long of a shift, or too short of a shift. But they wouldn't get any more specific.
On some vehicles with my scanner there is a parameter for "adaptable shift" which either "yes" or "no" -- if it is yes, then it can modify that adapt for that specific throttle position, I believe they are every 10 percent of throttle, for each gear, except for WOT (but would have to check with the scanner next time I have one to work on)

I have been told, but do not know for sure, that there is 4x more data to control the trans than there is for the engine. (and if I could clone my sts Cadillac or my 8.1/4l80e suburban transmission operation, I would and use that data on ALL transmissions. I LOVE the way both of those work)(although it could be the abundance of power in both of those)

when you take the boat trailer off the truck, it will shift rather firmly until it relearns the adapts (unless you have one new enough to have the "towing" button on the end of the shifter --- AND you use it.....)