Article Written By – Jason@JacFab
I’m writing this article for the site based on MY OWN experience using HP Tuners to modify the trans tune, your experiences may differ from mine. Tune at your own risk!
I’ll start by saying this is how I have, personally, gone about tuning the trans on my 2016 Camaro. It should be noted that the 2016 A8 transmission uses the T87 TCM, which can be tuned without all the extra hassle of having a 2017 and newer car which uses the T87a TCM. If you have a 2017 and newer, you will need to remove the TCM, and send it to HP Tuners to have it unlocked, and will also have to use extra credits when you get it back to license it to your tuning suite. I believe EFI Live is offering a similar service, so if you’re using anything other than HP Tuners, you will need to do some research. I imagine everything I’m talking about here will be similar to EFI Live, you might just have to poke around a little more to find the tables I reference.
I’ll start by addressing the Torque Management. Maybe people think that the Tq Mgmt is what holds back the car from achieving higher dyno numbers, or quicker times at the track. I feel that it does not, however in the future with future experimentationn, and hopefully if/when HP Tuners unlocks more tables within the A8, that may change how I feel. Once you open the trans section of your tune, click the TORQUE MANAGEMENT tab. On the left side of the window there will be a column that reads TORQUE REDUCTION. If YOU wish to disable the Tq Mgmt “completely” on the upshifts, change the UPSHIFT from ENABLE to DISABLE. I recommend changing POWER DOWNSHIFT to DISABLE, and change SPEED CTRL TERMINATE to IMMEDIATE
I PERSONALLY leave UPSHIFT tq mgmt enabled, as I find that the shifts can be completed quicker with it on, rather than off, but disabling it does give it quite a different shift feel that some may like. What we REALLY NEED is to be able to change the % of Tq Mgmt, but that isn’t currently available in HPT. It’s either on or off, so until that day comes we’re kind of stuck here.
You may also want to play with raising MAX TQ GEAR vs RPM under Toque Limit on the same tab. I populated the entire table with “750”.
The next this I will talk about is tuning the shift times. The shift times will be under TRANSMISSION > AUTO SHIFT PROPERTIES > SHIFT TIMES
I typically make Upshift POWER and upshift – PATTERN A the same, that way if I forget to put the car into Sport mode at the track, I don’t really lose anything. You will have to do some experimenting to see how quick you can get it to shift, each gear varies, and will only go so quick… If you try to make it shift too quick, bad things happen and you will think the transmission just fell out the back of your car. At the wide open throttle range, I ended up with mine between 0.050 to 0.100 quicker. Each gear is different, and I suspect each transmission will be different as no shift solenoid is the same as another. You see when the solenoid body is assembled, prior to assembly each shift solenoid is tested independently, and the data is stored in some magical GM cloud. If one, or multiple shift solenoids have to be replaced, the new programming must be done at a dealer (Or someone with an MDI and TIS access), and the solenoid data is pulled from the cloud and your TCM’s programming will be adjusted accordingly. So for this reason, no “MAX EFFORT” trans tune will be the same in one car as it is in another car. A canned tune will probably never get close to “MAX EFFORT”, so they’re probably all fine as they are not pushing things as hard as they can.
As you try to make the shifts quicker, you will need to raise the shift pressure. The shift pressure tab is right next to the shift time tab under auto shift properties. You will need to increase the max pressure, as well as each individual gear you want to make shift quicker. You will have to pay attention to each gear you are changing if the TCC is engaged or not, and change either the TCC ON, or TCC OFF section of the shift pressure.
To see if you need to increase shift pressure, or reduce shift time, you need to log TIME OF LATEST SHIFT, and go for a drive. If the time of latest shift is slower than what you commanded in the tune, try and raise the shift pressure. If that doesn’t help, odds are you are trying to command the shift to be faster than the transmission can mechanically do it, so back the shift time back down. Each gear seems to have it’s own limit, which is probably both a mechanical limit, but also still limited by the lack of available tables to adjust. You will also find that sometimes some gears will shift quicker than commanded. Not sure why, and not sure if it’s bad, but it’s obviously not slipping. Usually when this happens to me, it’s only shifting 0.025 quicker than commanded, and only in certain gears. Even though the trans is computer controlled, it’s still a mechanical device that can only do what it can do regardless of what the computer tells it. Again, shift pressure will seemingly vary by gear from my experience. No sense in throwing more pressure at it that it needs, and if you throw too much pressure at it, eventually there is a point of failure. If the max line pressure is too high, the trans cooler lines will start leaking, so watch for that. My individual shift pressures vary from +10% to +40% depending on the gear. I should also add that even when the car was completely stock, there is some slip during some of the shifts. If you want, you can start by logging the latest shift time, and comparing to the tune, add shift pressure until the slip goes away, then start modifying more from there. I imagine GM has this small amount of slip built in for “comfort”.
Something else you can play with is the SHIFT INERTIA, which supposedly controls the feel of the shift. I can’t say that I feel like I can notice a difference, but I changed it anyway, and it didn’t seem to negatively effect anything. Again, varies by gear in my tune, from +10 to +30% depending on the gear.
At some point should you decide to change the shift points, keep in mind that you will need to change both the full throttle shift RPM, and the shift MPH. Typically they need to somewhat correlate with each other, so do you logging to check your MPH and Speeds before starting to go down this road. I have only changed the 1-2, and the 2-3 shift points in my tune. I find that especially in first gear, I believe everything is happening so fast that you will need to continue to lower the shift MPH until you finally get the desired shift RPM, even if they seem very far apart compared to what you see in your logs. Even though its computer controlled, it still needs time to think.
I’m not going to get into it, but you can always play with the TCC settings.
-Jason @ JacFab.