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Discussion Starter #1 (Edited)
Transmission Adaptive Functions
(Source: AllData)​

The 4L60-E transmission utilizes a line pressure control system during upshifts to compensate for the normal wear of transmission components. By adjusting the line pressure, the PCM can maintain acceptable transmission shift times. This process is known as "adaptive learning" or "shift adapts" and is similar to the closed loop fuel control system used for the engine.

In order for the powertrain control module (PCM) to perform a "shift adapt," it must first identify if an upshift is acceptable to analyze. For example, upshifts that occur during cycling of the A/C compressor or under extreme throttle changes could cause the PCM to incorrectly adjust line pressure. When an upshift is initiated, a number of contingencies, such as throttle position, transmission temperature, and vehicle speed, are checked in order to determine if the actual shift time is valid to compare to a calibrated desired shift time. If all the contingencies are met during the entire shift, then the shift is considered valid and the adapt function may be utilized if necessary.

Once an adaptable shift is identified, the PCM compares the actual shift time to the desired shift time and calculates the difference between them. This difference is known as the shift error. The actual shift time is determined from the time that the PCM commands the shift to the start of the engine RPM drop initiated by the shift. If the actual shift time is longer than the calibrated desired shift time, a soft feel or slow engagement, then the PCM decreases current to the pressure control (PC) solenoid in order to increase line pressure for the next, same, upshift under identical conditions. If the actual shift time is shorter than the calibrated desired shift time, a firm engagement, then the PCM increases current to the PC solenoid in order to decrease line pressure for the next, same, upshift under identical conditions.

The purpose of the adapt function is to automatically compensate the shift quality for the various vehicle shift control systems. It is a continuous process that will help to maintain optimal shift quality throughout the life of the vehicle.

Clearing Transmission Adaptive Pressure (TAP)
Transmission adaptive pressure (TAP) information is displayed and may be reset using a scan tool.

The adapt function is a feature of the PCM that either adds or subtracts line pressure from a calibrated base line pressure in order to compensate for normal transmission wear. The TAP information is divided into 13 units, called cells. The cells are numbered 4 through 14. Each cell represents a given torque range. TAP cell 4 is the lowest adaptable torque range and TAP cell 14 is the highest adaptable torque range. It is normal for TAP cell values to display zero or negative numbers. This indicates that the PCM has adjusted line pressure at or below the calibrated base line pressure.

Updating TAP information is a learning function of the PCM designed to maintain acceptable shift times.
It is not recommended that TAP information be reset unless one of the following repairs has been made:

  • Transmission overhaul or replacement
  • Repair or replacement of an apply or release component, clutch, band, piston, servo
  • Repair or replacement of a component or assembly which directly affects line pressure

Resetting the TAP values using a scan tool will erase all learned values in all cells. As a result, the PCM will need to relearn TAP values. Transmission performance may be affected as new TAPs are learned. Learning can only take place when the PCM has determined that an acceptable shift has occurred. The PCM must also relearn TAP values if it is replaced.
 

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Gerry,

You are a fountain of knowledge. :thumbup:
 
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ah ha so gm does put brains to their tramys, isnt it also a good idea to reset them when you buy a old truck from a dealer? to adjust to your driving habbits?
 

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ah ha so gm does put brains to their tramys, isnt it also a good idea to reset them when you buy a old truck from a dealer? to adjust to your driving habbits?
Sounds like you wouldn't have to get a reset: "It is a continuous process that will help to maintain optimal shift quality throughout the life of the vehicle." It should 'learn' how the new owner drives. At least that's how I read it.
 

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Great information Gerry!
 

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Very cool, I figured the truck did something like this since after putting my shift kit in over 80k miles ago it feels like it's barely there. Guess the TAP could have been re-set then it woulda helped with the desired feel lasting longer, but it seems like this thing shouldn't be re-set or tampered with unless the conditions posted are completed.

But yeah cool shit.
 

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Gerry was able to adjust my line pressure and torque converter lock up for me at NESM 09. Wow, it was like new again!
 

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Spoolin Jr. Survivor
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so by "scan tool" you mean an obd2 code reader?
 

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So can aftermarket shops/tuners bypass this stuff and set them up for maybe 2 styles- "poart throttle" normal everyday driving for mileage & then a stomp it and go for maximum quickness ?
It seems to me that they have something similar built into my engine through a rev limiter - It will pull like crazy to around 60 or so, then fall flat..
 

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we have the same transmission as the saturn sky roadster and the pontiac solstice and they make a sick little shortie shifter for it. ill get the website name posted soon
 

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well put!
 

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So can aftermarket shops/tuners bypass this stuff and set them up for maybe 2 styles- "poart throttle" normal everyday driving for mileage & then a stomp it and go for maximum quickness ?
It seems to me that they have something similar built into my engine through a rev limiter - It will pull like crazy to around 60 or so, then fall flat..
I bet you anything it's your converter lock-up. These engines run better by keeping the converter unlocked at wot. My stock tune had my converter locking in second gear and changing that wade a world of a difference!
 

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we have the same transmission as the saturn sky roadster and the pontiac solstice and they make a sick little shortie shifter for it. ill get the website name posted soon
Wow, I hardly believe that the same transmision used for this work trucks can be suited in a light sport roadster like the solstice, maybe a Camaro or a Corvette, but not shure about a small car like those ones.
 

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Hi,i have a 2007 gmc canyon 4x4 with an automatique tranny...i want to know if someone had the same probleme i have...i just lost my reverse gear last friday and my dealler told me i might need a new one...please help.
 

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I bet you anything it's your converter lock-up. These engines run better by keeping the converter unlocked at wot. My stock tune had my converter locking in second gear and changing that wade a world of a difference!
mike which table needs to be adjusted to change the converter lock up? will doing that shorten the life of the converter/trans/fluid?

also, Gerry do you know how to disable adaptive shift pressure with HPT for guys who have servos installed to get the most out of them?
 

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mike which table needs to be adjusted to change the converter lock up? will doing that shorten the life of the converter/trans/fluid?

also, Gerry do you know how to disable adaptive shift pressure with HPT for guys who have servos installed to get the most out of them?
You want to keep adaptive shift pressure because that compensates for clutch pack wear. And I don't suggest locking the stock converter at wot.


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Discussion Starter #18
also, Gerry do you know how to disable adaptive shift pressure with HPT for guys who have servos installed to get the most out of them?
Yes, I do transmission tuning (for servos in particular) in many of my customers vehicles.
Just to be clear, I do not describe tuning as "disabling" systems... The systems are there for a reason.

Understand what the PCM/TCM is trying to do and understand what the aftermarket servo function is.

True tuning is a retraining of the PCM/TCM for its new mechanical conditions.. Just as GM calibrated for the OEM servos, you now have to calibrate for the aftermarket ones...
 

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I was looking to do the Servo upgrade. But is it still worth it being I can't tune because of the warranty. Will the transmission just adjust back to the original shifts.
 

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I was looking to do the Servo upgrade. But is it still worth it being I can't tune because of the warranty. Will the transmission just adjust back to the original shifts.
Servos technically void the warranty too; it all depends on if you own up to having servos and if you don't, the experience of the trans tech to identify aftermarket servos.

If you have a later-year truck that has adaptive shift, you will lose the effect of the servos until you remove adaptive shift. And if you're going as far as removing adaptive shift for the servos, why don't you just adjust the desired shift tables to decrease the shift time?
 
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