bmpcamry09
Well-Known Member
- Thread starter
- #1
Wanted to make a thread to spread some knowledge on our 8 speed. Specifically how the TCM operates and to clairfy the ever so often talked about "learning".
For years and years on various forums, people have made reference to the 8 speed saying it "learns" your habits, and if your having shifting issues, do a "relearn" or have your dealer reset adaptives to the car can "learn" how you drive. Well, this is only partially true and really isn't what everyone should be saying, and I'll show you why.
To start, every single JL or JT that hits the road from the factory has the exact same transmission calibration for your particular engine (2.0 does not have same trans tune as 3.6 for example). Same shift schedules, same parameters in the tuning, everything is the same. My 2025 3.6 is going to have the same trans tune as your 2025 3.6. Where the "Learning" side of these comes to play is NOT based on your driving behavior, but it is a built in TCM feature to adjust for natural discrepancies in manufacturing. TCM learning/adaptives are in place so that the TCM can adjust on the fly for minor differences in valve body clearances, valve body spring rates, clutch pack clearances, and other things that can slightly vary from model to model. This is why in factory service manuals after doing a valve body replacement will require programming and a learn procedure, because your fresh new valve body will not have the same internal characteristics as the old worn out one that was in there before. The adaptive/learning side of our transmissions is so that the transmission can produce consistent shift quailty for the life from the vehicle, even as clutches wear out, springs get softer, things expand and contract, etc.....by shift quality, I mean slip timers, ramp timers, fill timers, oncoming clutch timers, offgoing clurtch timers, and all aspects of the actual shift itself.
What these don't learn is your long term driving habits. So lets say you buy a used Jeep and you don't like how the transmission "bogs", it has NOTHING to do with the previous owner and their driving habits because the aggression tables are reset to the base level after every key off. Clearning adaptives or doing a quick learn is not going to change this. All that is going to do is force your TCM to relearn the wear and tear that your transmission has accomplished over the long term.
The "bogging" has everything to do with how your shift schedules are set up and has nothing to do with your previous owner. The ONLY driver based learning your TCM is doing is based on your current drive cycle. Our TCM uses a timer and an aggression based shift schedule set up. The timer activates based on throttle pedal position and acceleration rate. The TCM will spit out a shift table desired based on this timer, and will pick the appropriate shift type and schedule based on this timer. This timer goes back to 0 over time during your current drive cycle. This timer also resets to 0 after every engine start up event. There is NO long term adaptive for shift scheudle behavior. Below is a picture of the aggression tables within your TCM tune, and all of the boxes with numbers represent the various shift scheudles the transmission can pick from based on your "agression".....
The aggression counters and determined shift tables can be monitored with datalogging. As you can see below, I am datalogging most of the parameters that determine short term habits. "Shift ID" is what aggression table you are referencing. In the case of our Jeeps, table number 5, which is an aggression rate of 0, is the table referenced for 95 percent of normal daily driving. The longer you accelerate paired with how deep you are into your pedal will gradually move your aggression rate from 0 up to 4 (as seen above), and your shift schedules will change accordingly. THIS is the ONLY driver based habit learning your transmission does, and it is extremely short term and resets to 0 during your drive and after every key off.
Anyways, just a little nerdy breakdown for you guys.
What I am getting at is STOP resetting your adaptives with JSCAN or your scan tool. It is not needed, and it is forcing your TCM to have to relearn slip timers and all the mechanical aspects of your internals, and has nothing to do with driving habits.
As always, if you want a trans tune, hit me up or check out my tuning threads.
For years and years on various forums, people have made reference to the 8 speed saying it "learns" your habits, and if your having shifting issues, do a "relearn" or have your dealer reset adaptives to the car can "learn" how you drive. Well, this is only partially true and really isn't what everyone should be saying, and I'll show you why.
To start, every single JL or JT that hits the road from the factory has the exact same transmission calibration for your particular engine (2.0 does not have same trans tune as 3.6 for example). Same shift schedules, same parameters in the tuning, everything is the same. My 2025 3.6 is going to have the same trans tune as your 2025 3.6. Where the "Learning" side of these comes to play is NOT based on your driving behavior, but it is a built in TCM feature to adjust for natural discrepancies in manufacturing. TCM learning/adaptives are in place so that the TCM can adjust on the fly for minor differences in valve body clearances, valve body spring rates, clutch pack clearances, and other things that can slightly vary from model to model. This is why in factory service manuals after doing a valve body replacement will require programming and a learn procedure, because your fresh new valve body will not have the same internal characteristics as the old worn out one that was in there before. The adaptive/learning side of our transmissions is so that the transmission can produce consistent shift quailty for the life from the vehicle, even as clutches wear out, springs get softer, things expand and contract, etc.....by shift quality, I mean slip timers, ramp timers, fill timers, oncoming clutch timers, offgoing clurtch timers, and all aspects of the actual shift itself.
What these don't learn is your long term driving habits. So lets say you buy a used Jeep and you don't like how the transmission "bogs", it has NOTHING to do with the previous owner and their driving habits because the aggression tables are reset to the base level after every key off. Clearning adaptives or doing a quick learn is not going to change this. All that is going to do is force your TCM to relearn the wear and tear that your transmission has accomplished over the long term.
The "bogging" has everything to do with how your shift schedules are set up and has nothing to do with your previous owner. The ONLY driver based learning your TCM is doing is based on your current drive cycle. Our TCM uses a timer and an aggression based shift schedule set up. The timer activates based on throttle pedal position and acceleration rate. The TCM will spit out a shift table desired based on this timer, and will pick the appropriate shift type and schedule based on this timer. This timer goes back to 0 over time during your current drive cycle. This timer also resets to 0 after every engine start up event. There is NO long term adaptive for shift scheudle behavior. Below is a picture of the aggression tables within your TCM tune, and all of the boxes with numbers represent the various shift scheudles the transmission can pick from based on your "agression".....
The aggression counters and determined shift tables can be monitored with datalogging. As you can see below, I am datalogging most of the parameters that determine short term habits. "Shift ID" is what aggression table you are referencing. In the case of our Jeeps, table number 5, which is an aggression rate of 0, is the table referenced for 95 percent of normal daily driving. The longer you accelerate paired with how deep you are into your pedal will gradually move your aggression rate from 0 up to 4 (as seen above), and your shift schedules will change accordingly. THIS is the ONLY driver based habit learning your transmission does, and it is extremely short term and resets to 0 during your drive and after every key off.
Anyways, just a little nerdy breakdown for you guys.
What I am getting at is STOP resetting your adaptives with JSCAN or your scan tool. It is not needed, and it is forcing your TCM to have to relearn slip timers and all the mechanical aspects of your internals, and has nothing to do with driving habits.
As always, if you want a trans tune, hit me up or check out my tuning threads.
Sponsored
