This page is meant to answer some of the common file choice and drivability questions we see in the group. These are general recommendations. Your exact setup, tire size, driving style, fuel system, turbo setup, and how hard you work the truck will determine which file your truck should run.
1. Should I run medium pressure or high pressure?
For the majority of customers, we recommend medium pressure files.
Medium pressure files use plenty of clutch apply pressure to support the added torque from the horsepower files under normal driving conditions. For most daily driven trucks, tow rigs, and normal street-use setups, medium pressure gives the best balance of holding power, shift quality, and drivability.
High pressure files are not automatically “better.” They use a more aggressive clutch apply strategy and are generally intended for trucks that are driven hard regularly, especially on 125HP or higher files, or trucks with setups that are pushing the transmission harder than a normal daily driver.
High pressure files are better suited for max effort files, modified VGT or non-VGT turbo setups, bigger fuel setups, or trucks that are regularly raced, abused, or driven hard.
If your truck is mostly a daily driver, medium pressure is usually the right answer.
2. Should I run medium shift or high shift?
Shift RPM is mainly about driving experience and tire size, not about “better” or “worse,” or “correct” versus “incorrect.”
You do not have to run a higher shift RPM file if you do not want to. The elevated shift point files exist to help recover some of the effective gear ratio that is lost when you go to a larger tire.
When you install taller and heavier tires, the truck effectively becomes geared taller. That can make the truck feel lazier, make it lug the engine more, and keep it below the best part of the powerband during a lot of normal driving. A higher shift point helps keep the engine in a better RPM range so the truck can put power to the ground more effectively.
As a general recommendation, medium shift is usually best for trucks on roughly 35″ tires or smaller. High shift is usually best for trucks on roughly 37″ tires or larger.
This is not a hard rule. If you prefer the way one file drives over the other, run what feels best for your truck and driving style.
3. Should I run non-LBF, LBF?
This depends on how you want the truck to respond down low and whether smoke production is something you need to avoid.
Non-LBF is the cleanest and tamest option. It is a good choice for most daily drivers, tow rigs, stock turbo trucks, and people who want the least smoke and the most predictable low-speed behavior.
LBF adds additional fuel volume to the already existing factory low-boost fueling strategy. Low-boost fueling makes the truck feel more responsive at low RPM and helps the truck come into power quicker. It adds a noticeable amount of low-end torque below the turbo’s most efficient operating range. However, with added fuel before boost is fully built, smoke and EGTs can increase.
LBF files will generally produce a puff of smoke on the initial throttle tip-in that clears up as the turbo spools. LBF does not automatically mean more peak horsepower. It mainly changes how the truck responds before boost is fully built.
4. Why does my truck shift weird after loading a tune?
This is normal in most cases.
After loading a new engine or transmission file, the truck may need time to relearn. During the relearn process, the transmission may behave differently for a little while as it adjusts to the new shift strategy, torque output, pressure strategy, and converter behavior.
At first, you may notice slightly firmer shifts, odd downshifts, different converter lockup behavior, gear hunting, or shifts that improve after some drive time.
The best thing to do is drive the truck normally for a bit. Use light and moderate throttle, let it go through all the gears, and give it time to adapt. Do not immediately beat on it right after flashing and then judge the file based on the first few miles.
If the issue is severe, gets worse, feels like actual slipping, or does not improve after some drive time, then it needs to be looked at closer. At that point, a log, video, codes, and a good description of the concern are helpful.
5. Why does my truck make a shudder noise or feel like it is surging after I just uploaded your tunes?
The most common cause we see is the throttle valve still being plugged in when the setup requires it to be unplugged.
The throttle valve can create a shudder, rumble, flutter, or surging feeling in certain conditions, especially at light throttle, low RPM, or during transitions where airflow is being managed. Since its operation has been revised in the tune, leaving it plugged in on a setup that requires it to be unplugged can create weird drivability issues that people often mistake for a transmission problem.
6. Do I need a transmission tune?
On trucks running added power, yes, a transmission tune is strongly recommended.
The engine tune increases torque. The transmission tune helps the truck manage that added torque with better shift scheduling, converter strategy, and clutch apply pressure.
Running more power without proper transmission tuning can make the truck feel lazy, luggy, inconsistent, or harder on the transmission than it needs to be.
7. Is high pressure harder on the transmission?
High pressure is not “bad,” but it is not needed for everyone.
More apply pressure can increase clutch holding capacity, but it can also make the truck shift firmer and feel more aggressive. That is useful on higher power setups or trucks that are driven hard, but it is unnecessary for most normal daily drivers.
This is also why our pressure strategy is not just about maxing out line pressure everywhere. A lot of the focus is on controlling clutch apply pressure and shift behavior in the areas where it is actually needed.
And no, high pressure is not a fix for a worn or slipping transmission. If the transmission already has a mechanical issue, a tune is not going to magically repair it.
8. Do I have to match raised shift with high pressure?
No.
Shift point and pressure are two separate choices. Pressure is about clutch apply and holding power. Shift point is about RPM, tire size, gearing, and driving feel.
For example, a truck on 37s may do great with a medium pressure and raised shift file. A truck on smaller tires that is driven hard may prefer high pressure and medium shift.
Pick the file based on how the truck is used, not just because the names sound like they should match.
9. What file should I tow on?
We know most of you guys are not data nerds like us and are not interested in constantly monitoring EGTs. And honestly, why should you have to? You paid $60k+ for a tool. It should work reliably and safely when you need it to.
For that reason, we recommend stepping down to the specified tow tune for your generation truck when towing.
Those files are built with towing, temperature control, drivability, and reliability in mind. The goal is to let the truck work like it is supposed to without the customer needing to constantly worry about EGTs or whether they are pushing the setup too hard.
That does not mean you should intentionally abuse the truck, lug it in too high of a gear, or ignore obvious issues. It simply means the tow files are the correct choice when the truck is being used as a truck.
10. Why does my truck feel different after changing tire size?
Larger tires effectively change the gear ratio of your truck. This can make the truck feel slower, make it shift sooner than you want, and make the engine lug more at low RPM.
That is why we recommend higher shift point files for larger tire setups. It helps put the truck back into a better operating range.
11. What should I do if the tune does not feel right?
Before assuming something is wrong with the tune, check the basics.
Make sure the correct file was loaded, check for codes, check fuel quality, check fuel filters, check for boost leaks, check for exhaust leaks, make sure tire size and setup match the file recommendation, and give the transmission time to relearn after flashing.
If the issue continues, send useful information to the people who developed the tunes. Not Joe Blow the Powerstroke King, not another company, and not a random comment section full of people guessing.
“It shifts weird,” “it feels off,” or “it’s banging gears at WOT” is hard to diagnose by itself. A video, codes, current file, tire size, truck year, mods, and a good description help us immensely when it comes to troubleshooting.
12. Can I switch power levels while driving?
Yes, if your truck has SOTF and it is set up correctly, you can switch power levels while driving.
That said, do not switch levels while you are wide open throttle or beating on the truck. Make the change under normal driving conditions and give the truck time to learn the transition before you beat the brakes off of it.
13. Are firmer shifts normal?
Yes, to a point.
A tuned transmission will often shift firmer than stock because it is applying the clutches quicker and more confidently. A firm shift is not automatically a problem.
However, there is a difference between a firm shift and a harsh bang, flare, slip, or delayed engagement. If it feels abnormal or violent, get a video and send details so it can be looked at properly.
14. What information should I include when asking for help?
Please include the truck year, tire size, current engine file, current transmission file, whether you are running non-LBF, LBF, any codes present, what speed, gear, and RPM the issue happens at, whether it happens hot or cold, loaded or unloaded, towing or empty, and a clear video if possible.
The more information you provide, the easier it is to give you a real answer instead of guessing.
15. What is the difference between TCM Adaptive Table Reset and TCM Relearn?
These two functions are not the same thing.
TCM Adaptive Table Reset clears the learned transmission adaptive data. Over time, the TCM learns clutch apply timing, fill time, pressure corrections, shift behavior, and converter behavior based on how the transmission responds. Resetting the adaptive tables clears those learned values and puts the TCM back closer to a fresh baseline.
This can be useful after loading a different transmission file, replacing or rebuilding a transmission, doing valve body work, replacing solenoids, or when specifically instructed to do so while troubleshooting.
TCM Relearn is different. In the Auto Agent functions menu, TCM Relearn is generally used to make the TCM recognize a configuration change that was made elsewhere in the truck.
For example, if you change tire size or gear ratio, that information is being changed in the BCM first. Running the PCM Relearn and TCM Relearn helps force the PCM and TCM to recognize that updated vehicle configuration.
3 times when an adaptive relearn should be used:
– Going from stock TCU tuning to CMB Performance TCU tuning.
– Going from another company’s TCU tune to CMB Performance tunes.
– If your transmission is still presenting a characteristic you don’t like after the 500 mile learning phase.
GET IN TOUCH
Use the button below to email us!