HP Tuner for 2016 Tahoe L83/6L80

[RobH]

I want to get the Active Fuel Management (AFM)/Displacement on Demand (DOD) turned off in my 2016 Tahoe. At the moment I am driving with the transmission in M5 which prevents V4 operation. If I operate the transmission in M6, AFM remains disabled in 1st - 5th gears, but in 6th the AFM is enabled again and switches back and forth from V8 to V4 to V8, etc. I use the OBDII port for my ScanGauge II, so I don't want an AFM Disable dongle.

I am considering the HP Tuner. I also would like to modify Torque Converter Clutch (TCC) engage and disengage speeds, shift speeds, set the TCC slip to zero, etc. I am not looking to alter engine ignition and fuel tables. I have enough power. I just want to perform the AFM disable and change the way the transmission behaves.

With our 1995 Chevy Caprice and 1995 Buick Roadmaster, I used Tuner Cat software on my laptop to download the PCM settings files, edit the files, and then load the settings files back up to the cars' PCM's using the cars' OBDI connection port.

Looking at the HP Tuners (HPT) website, it looks like the HPT MPVI3 OBDII Interface module, VCM Suite software, and 2 credits (activity authorizations) are needed. My understanding is that I can use the HP Tuner in the same way I used the Tuner Cat software on our 1995 cars.

But, I see something on the HP Tuner website that suggests that the MPVI3 and VCM Suite will only allow me to modify the operation of the ECM (Engine Control Module) and not the TCM (Transmission Control Module). Is this true? Am I unable to modify the transmission behavior? Do I need to buy additional software, hardware, or credits to modify the transmission shifting?

I am not currently considering Black Bear Performance because I sent them a PM a week and a half ago on this Forum with no response. I sent them a message on their website a week ago with no response. It appears that I will need to go back to them to get fine tuning of my transmission's behavior. I want to be able to make my modifications, go out and drive the car, and then fine-tune the transmission's behavior without having to wait a week or more or several weeks for updates to my "Tune" (settings file). I understand that BBP may have more business than they can handle. If so, that is good for them and bad for me as a prospective customer.

Thanks in advance for advice.

 

[swathdiver]

Well I was beginning to type in @BlackBearPerf until I got to the bottom of your post.

When I was in your shoes, I chose to take advantage of Justin's decades of tuning experience instead of using my daily driver as the guinea pig for my learning curve. My learning curve can be steep!

Since he's done such a tremendous job on my trucks, I never bothered with doing it myself though it is something I like to do. He's done two so far and I have one more coming up when it cools down in the fall.

 

[BlackBearPerf]

I want to get the AFM turned off in my 2016 Tahoe. At the moment I am driving with the transmission in M5 which prevents V4 operation. If I operate the transmission in M6, AFM remains disabled in 1st - 5th gears, but in 6th the AFM is enabled again and switches back and forth from V8 to V4 to V8, etc. I use the OBDII port for my ScanGauge II, so I don't want an AFM Disable dongle.

I am considering the HP Tuner. I also would like to modify Torque Converter Clutch (TCC) engage and disengage speeds, shift speeds, set the TCC slip to zero, etc. I am not looking to alter engine ignition and fuel tables. I have enough power. I just want to perform the AFM disable and change the way the transmission behaves.

With our 1995 Chevy Caprice and 1995 Buick Roadmaster, I used Tuner Cat software on my laptop to download the PCM settings files, edit the files, and then load the settings files back up to the cars' PCM's using the cars' OBDI connection port.

Looking at the HP Tuners (HPT) website, it looks like the HPT MPVI3 OBDII Interface module, VCM Suite software, and 2 credits (activity authorizations) are needed. My understanding is that I can use the HP Tuner in the same way I used the Tuner Cat software on our 1995 cars.

But, I see something on the HP Tuner website that suggests that the MPVI3 and VCM Suite will only allow me to modify the operation of the ECM (Engine Control Module) and not the TCM (Transmission Control Module). Is this true? Am I unable to modify the transmission behavior? Do I need to buy additional software, hardware, or credits to modify the transmission shifting?

I am not currently considering Black Bear Performance because I sent them a PM a week and a half ago on this Forum with no response. I sent them a message on their website a week ago with no response. It appears that I will need to go back to them to get fine tuning of my transmission's behavior. I want to be able to make my modifications, go out and drive the car, and then fine-tune the transmission's behavior without having to wait a week or more or several weeks for updates to my "Tune" (settings file). I understand that BBP may have more business than they can handle. If so, that is good for them and bad for me as a prospective customer.

Thanks in advance for advice.

That is odd. We didn't receive your PM here and we are only a few days back on email. Please send the email again. We are more than happy to review it for you.

 

[Trey Hardy]

I want to get the AFM turned off in my 2016 Tahoe. At the moment I am driving with the transmission in M5 which prevents V4 operation. If I operate the transmission in M6, AFM remains disabled in 1st - 5th gears, but in 6th the AFM is enabled again and switches back and forth from V8 to V4 to V8, etc. I use the OBDII port for my ScanGauge II, so I don't want an AFM Disable dongle.

I am considering the HP Tuner. I also would like to modify Torque Converter Clutch (TCC) engage and disengage speeds, shift speeds, set the TCC slip to zero, etc. I am not looking to alter engine ignition and fuel tables. I have enough power. I just want to perform the AFM disable and change the way the transmission behaves.

With our 1995 Chevy Caprice and 1995 Buick Roadmaster, I used Tuner Cat software on my laptop to download the PCM settings files, edit the files, and then load the settings files back up to the cars' PCM's using the cars' OBDI connection port.

Looking at the HP Tuners (HPT) website, it looks like the HPT MPVI3 OBDII Interface module, VCM Suite software, and 2 credits (activity authorizations) are needed. My understanding is that I can use the HP Tuner in the same way I used the Tuner Cat software on our 1995 cars.

But, I see something on the HP Tuner website that suggests that the MPVI3 and VCM Suite will only allow me to modify the operation of the ECM (Engine Control Module) and not the TCM (Transmission Control Module). Is this true? Am I unable to modify the transmission behavior? Do I need to buy additional software, hardware, or credits to modify the transmission shifting?

I am not currently considering Black Bear Performance because I sent them a PM a week and a half ago on this Forum with no response. I sent them a message on their website a week ago with no response. It appears that I will need to go back to them to get fine tuning of my transmission's behavior. I want to be able to make my modifications, go out and drive the car, and then fine-tune the transmission's behavior without having to wait a week or more or several weeks for updates to my "Tune" (settings file). I understand that BBP may have more business than they can handle. If so, that is good for them and bad for me as a prospective customer.

Thanks in advance for advice.

There’s plenty of tuners in Texas that could do it and I don’t know how far you are from Texas speed performance but they were my first thought I’m sure you could find one local though if you called around at the performance shops near you

 

[RobH]

I'm a retired IT guy. So I know my way around programming.

I understand that the companies that provide the software to download the Engine Control Module (ECM) and Transmission Control Module (TCM) settings files ("tunes" or "calibrations"), edit the files, and then upload the modified settings files back to the ECM/TCM need to get payment for the value they are providing. Otherwise they wouldn't do it and we'd be stuck with what the auto manufacturers give us, warts and all.

Now the companies that analyze our ECM's, TCM's, etc. to write their proprietary software to display and edit the settings files have inserted a hardware interface in between our laptop and our ECM's/TCM's. That way they have something physical they can sell in addition to their software. OK. And it makes it difficult for me to send a custom file to a friend, since they need the hardware interface module/credits to load the custom file into their car. OK.

But, I know how to do the file downloading, editing, and uploading. I have researched what settings I want to make. HP Tuners has YouTube videos on how to shut off the AFM/DOD in the ECM and to modify/improve the 6L80 files using their software. The current version includes data logging. I don't need to drive to a tuner to have the tuner make the changes or send me an off the shelf "tune" which does things I don't want it to do and doesn't do things that I do want it to do.

In my dragstrip days, after twice breaking my daily driver's differential spider gears, I decided I didn't want to spend the time and money to do that. I'm past my street enthusiastic driving days when I regularly got tickets. I now drive for longevity and no tickets.

So, my original question. If I buy HP Tuners' MPVI3 OBDII Interface module, VCM Suite software, and 2 credits can I shut off my AFM in the ECM and adjust my transmission (TCM) behavior? Summit Racing will be happy to sell me the interface module, the cable between the interface module and my OBDII port, and "credits". Or do I have to buy something else to edit my 2016 Tahoe TCM settings file?

Thanks in advance.

 

[randeez]

you would need to buy additional credits to unlock the tcm and make modifications, in addition to the credits needed to unlock the ecm to make the modifications to disable afm.
you can still send the file to anyone, downloading the vcm suite is free for anyone and they can view a tune file you send them. if they want to make changes and save the changes then they would also need license the tune (credits associated to an mpvi)
its a farcry from the ol tunercat days tho, steep learning curve... especially playing around with transmission pressure settings, lockup and shift points can still be laid out with the bluecat tool as it has been updated for 6-8-10 speeds

 

[RobH]

you would need to buy additional credits to unlock the tcm and make modifications, in addition to the credits needed to unlock the ecm to make the modifications to disable afm...its a far cry from the ol tunercat days tho, steep learning curve...especially playing around with transmission pressure settings, lockup and shift points can still be laid out with the bluecat tool as it has been updated for 6-8-10 speeds.

Thank you. I suspected something like more credits for the TCM.

Thanks again.

Edit: It turns out that only two credits are required to modify both the ECM and TCM calibration files on the 2016 Tahoe.

 

[swathdiver]

Thank you. I suspected something like more credits for the TCM.

Thanks again.

Keep us posted on how everything works out.

We run our trucks at the drags and don't like breaking things either. I skip the burnouts and just launch off idle. She's faster that way anyway.

 

[tooleyondeck]

Should be 4 credits total. I use my MPVI2+ on all my vehicles, definitely a recommended purchase.

 

[RoadTrip]

you would need to buy additional credits to unlock the tcm and make modifications, in addition to the credits needed to unlock the ecm to make the modifications to disable afm.
you can still send the file to anyone, downloading the vcm suite is free for anyone and they can view a tune file you send them. if they want to make changes and save the changes then they would also need license the tune (credits associated to an mpvi)

Can HPTuners give access to the BCM via extra credits? I've had no luck finding anyone who will make a couple changes for me to the BCM.

 

[RobH]

Sorry @RoadTrip, don't know about the BCM. But, I may have an answer in a couple of weeks. Edit: I sent you a PM.

I bought an HP Tuners (HPT) package with two credits from Summit Racing.

Edit: Two credits will allow me to update both my 2016 Tahoe LT's Engine Control Module (ECM) and 6L80 Transmission Control Module (TCM).

1. First I will disable the AFM to hopefully avoid one of the AFM lifters failing and taking out the camshaft, killing the engine. That will also allow me to resume using sixth gear for highway cruising. HPT has a YouTube video on modifying the ECM to disable the AFM. It should be simple.

Edit: If I keep the Tahoe past this summer, I may do an AFM "delete kit" to replace the inactive AFM hardware with standard lifters, camshaft, etc.

2. HPT has a YouTube video on modifying the TCM settings/parameters/calibration file to modify the 6L80 behavior.

I'll set the TCC target slip to 0 RPM in all the gears.

Apparently the TCM allows some slippage some or most of the time to make the engine/transmission package "smoother" and to mask the AFM switching back and forth from V8 operation to V4 operation. The TCC slippage creates heat and wears the TCC friction surfaces. When the TCC becomes metal on metal, goodbye transmission. Apparently I was fortunate my transmission lasted 121K miles.

Many people advocate disabling TCC lockup in gears 1-4. I don't plan to do that. With the TCC unlocked, the churning of the fluid in the torque converter creates heat. I'm in South Texas with summer six months of the year. My reman transmission does have the transmission service bulletin 70C/158F Thermal Bypass Valve (TBV) thermostat. My transmission temps are now running 145-160F.

3. Next, I'll raise the shift speeds and TCC lockup speeds to avoid the transmission having the engine running at 1,200 to 1,500 RPM with the TCC locked up in 6th gear instead of higher RPM in 5th gear. I know that low RPM and high manifold pressure may be a little more miles per gallon. But, I am interested in miles per engine and not having the engine give me problems away from home on a trip.

Same applies to the lower gears' upshifts and TCC lockup speeds. I'll also be adjusting the TCC unlock and downshift speeds. I did this on my 1995 Chevy Caprice. My target is the engine operating between 1500 and 2000 RPM around town and up to 2500 RPM when I am pressing harder on the loud pedal. If I want to go above 2500 RPM, I can use the +/- transmission switch on the shift lever.

I know that I can shorten the shift times and increase line pressures. I may experiment carefully with those. I'm looking for longevity, not quick (hard or harsh) shifts.

I will report my progress in this thread. I appreciate everyone's input. Maybe @NickTransmissions will let me know if I'm going astray.

 

[yugrus]

Have you looked into OBD2 splitter? You can then use both your ScanGauge and the AFM disable dongle.

 

[kaiserwillie]

Have you looked into Diablosports I3 tuner? I got one for my 2016 Yukon to disable AFM/DOD thru a tune and it works like a charm. It also can make changes to the TCM which I will be looking into to try and preserve the tranny.

 

[buckwild27]

Sorry @RoadTrip, don't know about the BCM. But, I may have an answer in a couple of weeks.

I was unable to get a clear answer from HP Tuners on whether buying two "credits" will give me the capability to change both the Engine Control Module (ECM) and the Transmission Control Module (TCM) or just the ECM. I am getting an HP Tuners package with two credits via UPS from Summit Racing later today.

1. First I will disable the AFM to hopefully avoid one of the AFM lifters failing and taking out the camshaft, killing the engine. That will also allow me to resume using sixth gear for highway cruising. HP Tuners has a YouTube video on modifying the ECM to disable the AFM. It should be simple.

If I keep the Tahoe past this summer, I may do an AFM delete kit to remove the inactive AFM hardware.

If two credits will not allow me to update the 6L80 TCM behavior, I'll order two more credits from Summit Racing. HP Tuners has a YouTube video on modifying the TCM settings/parameters/calibration file to modify the 6L80 behavior.

2. I'll set the TCC target slip to 0 RPM in all the gears. Apparently the TCM allows some slippage some or most of the time to make the engine/transmission package "smoother" and to mask the AFM switching back and forth from V8 operation to V4 operation. The TCC slippage creates heat and wears the TCC friction surfaces. When the TCC becomes metal on metal, goodbye transmission. Apparently I was fortunate my transmission lasted 121K miles.

Many people advocate disabling TCC lockup in gears 1-4. I don't plan to do that. With the TCC unlocked, the churning of the fluid in the torque converter creates heat. I'm in South Texas with summer six months of the year. I do have the transmission service bulletin 70C/158F Thermal Bypass Valve (TBV) thermostat. My transmission temps are now running 145-160F.

3. Next, I'll raise the shift speeds and TCC lockup speeds to avoid the transmission having the engine running at 1,200 to 1,500 RPM with the TCC locked up in 6th gear instead of higher RPM in 5th gear. I know that low RPM and high manifold pressure is a little more miles per gallon. But, I am interested in miles per engine and not having the engine give me problems away from home on a trip.

Same applies to the lower gears' upshifts and TCC lockup speeds. I'll also be adjusting the downshift and TCC unlock speeds. I did this on our 1995 Chevy 9C1 ex-highway patrol Caprice and Buick Roadmaster. My target is the engine operating between 1500 and 2000 RPM around town and up to 2500 RPM when I am pressing harder on the loud pedal.

I know that I can shorten the shift times and increase line pressures. I may experiment carefully with those. I'm looking for longevity, not hard or harsh shifts.

I will report my progress in this thread. I appreciate everyone's input. Maybe @NickTransmissions will let me know if I'm going astray.

Did you try these guys for bcm tuning?
They do require you have an Autosync.

BCM (Global-A)

Body Control Module (BCM) programming for all GM “Global-A” trucks/SUVs. Exclusively available from CCE, this programming will allow you to customize hundreds of parameters in your vehicle’s BCM and add new features as well! You must already own an AutoSync third-party programmer device (google...

www.customcalibrationengineering.com

 

[RobH]

Per my post # 11 above, I have already decided to ride the HP Tuners (HPT) horse, a result of my online research and viewing videos which showed the HPT product in use. From here on, please let's use this thread to describe my experience for others who may be considering the HP Tuners product. I'll also answer questions about the HPT product.

So far, my experience with HPT's MPVI3 interface module and the HPT VCM Suite software has been positive. My Tahoe's AFM/DOD is no longer active, I've told my ECM and TCM to use the diameter of my current tires for speed calculations, and I've set my Torque Converter Target Slip RPM values to Zero in all six gears.

Apparently, HPT wholesales their current interface module, the MPVI3, with the serial number sometimes already having "credits" attached. When I got the box from Summit Racing, the HPT box contained
1. the MPVI3 OBDII interface module,
2. a cable with a male UPS plug at one end and a jack which fits into the MPVI3 at the other end, and,
3. a Quick Start Guide.

The MPVI3 interface module has a plug which connects to the Tahoe's OBDII port under the dash just to the left of the steering column. I bought a $16 OBDII extension cable which I do not need.

1. I followed the instructions on the Quick Start Guide to register the MPVI3 with HP Tuners. The Quick Start Guide next told me to download and install HPT's VCM Suite which contains the VCM Editor and Scanner. It also told me to create an account with HPT. Next was associating my MPVI3 interface device with my HPT account. At this point, HPT told me that I had two credits on my account.

My two credits were sufficient to load changes to both my Tahoe's Engine Control Module (ECM) and Transmission Control Module (TCM).

With the registered VCM interface device and HPT VCM software, a control module calibration file can be downloaded from my Tahoe, viewed, edited, and saved to my computer without credits. Credits are required to write a modified calibration file to my Tahoe's ECM or TCM.

My laptop is running Windows 10.

2. Caution: Before copying my Tahoe's ECM calibration file into VCM editor on my laptop, I made sure that the Tahoe's battery and my laptop's battery were fully charged. In fact, I replaced my five year-old Tahoe battery with a new battery five days ago, so it was strong and freshly charged. My laptop has a strong battery which allows it to run for several hours; it was freshly topped off. The goal is to be able to copy the vehicle file without a hiccup and to write the modified calibration file to the vehicle without a hiccup.

Caution: Note that I said nothing about having a battery charger on my Tahoe or my laptop. Chargers can introduce extraneous signals on the charging lines which might disrupt a read or a write. I said "can" and "might", not "will". If the read or write is disrupted, a new dealer installed and initialized control module may be required. So, I suggest that care be taken on the batteries.

I then copied my Tahoe's ECM calibration file into my VCM Editer on my laptop. The first thing I did after copying my ECM file into VCM editor was save the file in my laptop's Tahoe/HPT/ECM directory as
"0_Chevy_Factory_ECM_File.hpt".
The file extension ".hpt" is for an HPT proprietary file format. That way I have a copy of what Chevy put in my Tahoe. I can write it back to my ECM if I get out in left field with a modified calibration file. I'll back up the directory to a thumb drive which I keep in my safety deposit box.

3. I next went to the Gear/Tire Wizard on the Edit tab in VCM editor and entered the diameter (height) of my tires and told the Wizard to udate my control module.

4. Using the principles described in this HPT YouTube Video,

I switched the AFM/DOD behavior choice from "Enable" to "Disable". Unlike the video, that was the only calibration item on the screen. I saved the ECM calibration file with the name "1_DOD_Disable_Basic.hpt" in the same directory as before.

I then saw a choice under the Edit tab / View tab to perform Basic or Advanced editing. Basic was selected. I clicked on Advanced and subsequently saw an edit screen which mostly matched the screen shown in the YouTube videos. I made the changes suggested in the YouTube video and saved the file in the same directory as before, assigning the name "2_DOD_Disable_Advanced.hpt".

5. I now had a file with the desired changes ready to write back to my Tahoe. When I tried to do so, VCM Editor said that I didn't have credits to do so. What it really meant was that I didn't have credits identified/selected to do so. I went to my HPT account and selected the credits that were on my account and wrote the ECM calibrations file to my Tahoe.

The first part of the writing step appeared to be an erasing of the calibration file loaded in the ECM. Perhaps that was required to provide room for my modified file to be written to the ECM. The file was successfully written. Whew.

6. I followed much the same process to set the target Torque Converter slip to zero. I will put more detail on it in the next post on this thread tomorrow.

7. With AFM disabled, I can now use sixth gear on the highway, perhaps without adding more wear to my AFM lifters. The zero'ed out Torque Converter Clutch target slip may help my reman transmission's Torque Converter Clutch last longer, hopefully much longer.

After replacing the battery, the dashboard center display showed the outside air temp as 47F which was incorrect. It also showed a bad time. I reset the date and time. Over a period of maybe thirty minutes driving, the outside temperature came up to something reasonable.

After writing my modified ECM and TCM calibration files to my Tahoe, the ignition was ON, as needed for writing to the vehicle. When I disconnected the MPVI3 and tried to start the engine, it would not start. I turned the ignition OFF by pushing the Start/Stop button. I waited about a minute, then turned the ignition ON and the engine started normally.

I like the way the vehicle is driving, without the delay when switching from driving on the flat in V4 mode and then starting up a hill and switching to V8 mode.

 

[RobH]

Vehicle Control Module "programming" rough explanation.

I don't know the actual approach that GM used. Typically there is an operating program installed/written in the control module, be it the Engine Control Module, ECM, which is a box in the engine compartment, the Transmission Control Module, TCM, which I believe is in the 6L80 transmission, the BCM or, in the CCM, which I is a module which changes the exhaust sound and/or controls the Corvette exhaust bypass valve. In my 1995 Caprice, all of the functionality was in the Powertrain Control Module (PCM) in the engine compartment. Vehicle computer management has progressed since then.

When the vehicle is powered up, the control modules load their operating programs into active memory. The programs have instructions for how to do their jobs. If a program does not have instructions for accessing and displaying transmission temperature, it doesn't even think about it.

I don't know what human readable programming language is used. In any case, the human readable programming language is probably compiled (translated) into a compact but humanly unreadable form. For HP Tuners to allow us to modify things like AFM disable, the unreadable form has to be reverse engineered into a readable form. That is a value that the tuner companies like HP Tuners, Diablo, etc., bring to the table.

The first thing the individual control programs do after powering up is read it's stored calibration file to get its operating parameters. For instance, whether to enable or disable AFM. How long to let a remote start event to continue. If the operating program does not have instructions to get the remote start continue time from the calibration file and use it, it isn't going to happen.

The next piece of value the tuner companies like HP Tuners bring to the party is a formatted editing program, in this case the VCM Editor. It reads a calibration file and lays out on the screen various parameters which the user can modify/edit. Like whether to enable or disable the AFM completely. Whether to make the AFM inoperative below a VSS of 50 or some other speed like 250 miles per hour, etc.

Typically, the calibration file editor can write a modified calibration file to a directory in the end user's computer (my laptop) or through the OBDII connector into the vehicle's control module. Reading and overwriting the control modules' calibration files through the OBDII connector is another piece of functionality the tuner companies bring to the marketplace.

There is enough demand for playing with the engine and transmission that it is worthwhile for the "tuner" companies to go into the ECM and TCM and figure out what is going on.

Unfortunately, if there is not enough marketplace demand, a given service will not be offered. The HP Tuners VCM Editor only offers to read, edit, and write the Tahoe's ECM, TCM, and CCM calibration files.

When we load "tunes" into our vehicle's control modules, we are overwriting a control module's calibration file.

 

[RobH]

I used the following video for information on how to modify my transmission's Transmission Control Module (TCM) to set the target slip for the Torque Converter clutch (TCC) to zero.

HPT 6L80 Tuning 101

After replacing the Tahoe battery, before doing any HPT stuff, the dashboard center display showed an incorrect time and the outside air temp as 47F which was incorrect, the outside air was in the low nineties. I reset the date and time. Initially, the air conditioner was not blowing cold air with the desired temp set at 75F. Maybe it figured that with an outside temp of 47F all I needed was outside air (which was actually in the low nineties). Over a period of maybe thirty minutes of driving, the outside air temperature indication came up to something reasonable and the air conditioner started working normally.

After writing my modified ECM and TCM calibration files to my Tahoe, the ignition was ON, as needed for writing to the vehicle. When I disconnected the MPVI3 and tried to start the engine, it would not start. I turned the ignition OFF by pushing the Start/Stop button. I waited about a minute, then turned the ignition ON and the engine started normally. The time was OK, but the outside air temp was showing 32F. Again, it came up to something reasonable after some driving and the air conditioner started working normally.

That's my story and I'm sticking to it.

 

[RobH]

This post describes my using the HPT VCM Editor for customizing upshift and downshift speeds in each of the six gears. My goal was to avoid putting a load on the engine at low RPM ("lugging the engine"). I can still use the Manual mode with the up and down rocker switch on the shift lever if I want to delay shifts until a higher speed or force a downshift.

DISCLAIMER OF LIABILITY: Use the information in this post at your own risk. This post is not a tutorial. I am only reporting what I did. It is possible to damage your engine and/or transmission by altering factory settings.

I did not try to change shift quickness, pressures, or firmness. My goal is maximum miles per engine and transmission, not maximum "performance".

In the VCM Editor, with a TCM file loaded, I clicked on the "Trans" tab, and then on "Shift Schedules". I spent a lot of time looking at the way the Factory TCM managed the Shift Schedules. There are three main schedules, Normal, Pattern A, and Pattern B. Normal and Pattern B were almost but not quite the same. Pattern A in the factory TCM appeared to describe the way my Tow/Haul mode was managing the transmission. This contradicted the apparent use of Pattern A and Pattern B as depicted in the "Trans/Shift General/Shift Pattern Type" display.

Normal, Pattern A, and Pattern B each have tables which give the speeds at which shifts occur as a function of Throttle Position as a percent of 100%.

The various tables are
Upshift: 1->2, 2->3, and 3->4 upshift speeds.
Downshift: 2->1, 3->2, and 4->3 downshift speeds.
Upshift 5th: 4->5 upshift speeds.
Downshift 5th: 5->4 downshift speeds.
Upshift 6th: 5->6 upshift speeds.
Downshift 6th: 6->5 downshift speeds.

My Normal and Pattern B upshift Speeds were at a lower speed than I wished, so I set
1->2 upshifts at 13 MPH where they were lower.
2->3 upshifts at 22 MPH where they were lower.
3->4 upshifts at 38 MPH where they were lower.
4->5 upshifts at 48 MPH where they were lower.
5->6 upshifts at 64 MPH where they were lower.

I set the downshift speeds at a couple of MPH lower than the upshift speed for each of the Throttle Position percents. I checked and rechecked that a downshift speed is ALWAYS LOWER than the upshift speed. For instance, when I upshift from 2->3, I do not want the transmission to fight itself upshifting and then immediately downshifting 3->2, upshifting 2->3, downshifting 3>2, etc.

I created a copy of the Factory TCM file so that I could keep checking to make sure that I was followig the pattern of the factory settings, just uniformly increasing them where they were less than I desired.

Another thing I kept checking, is that an upshift was not followed by an immediate upshift. For instance, I set the mph for a shift from 3->4 greater than the mph for a shift from 2->3 at all Throttle Position percents, so that the TCM would not try to shft from 2nd gear directly to 4th gear. The same thing applied to a downshift. For example, I made sure that some MPH reduction was required after a downshift from 4->3 before a downshift from 3->2. I studied how the Shift Schedules tables in my Factory TCM file are configured before making changes to the files I was going to write to my TCM.

For Pattern A, which appeared to be for my Tahoe's Tow/Haul mode, I wanted it to shift at a little lower speed than it was with my 3,300 pound trailer, to not rev as high in 1st before shifting to 2nd, etc., so I changed
1->2 at 15 MPH across the table through 44% Throttle Position (%).
2->3 at 22 MPH across the table through 31% Throttle Position (%).
3->4 at 38 MPH across the table through 25% Throttle Position (%).
4->5 no change.
5->6 at 68 MPH across the table through 31% Throttle Position (%).

I cruise at 60 MPH while towing on the level. I may accelerate to 65 to 70 MPH when going down a longer hill. While towing, I don't want the transmission in 6th below 66 MPH.

Final cruise speed may be modified depending on wind speed and direction. Final cruise speed may be adjusted depending on other safety factors.

If I had a heavier trailer, I might not have reduced any upshift speeds. I might have increased some.

Again, I set the downshift speeds two MPH below the upshift speeds for each of the upshift Throttle Position percents. I ENSURED that the downshift MPH is less than the upshift MPH for each of the Throttle Position percents. I don't want the transmission to upshift from any gear to a higher gear and then immediately downshift back to the lower gear.

I did not change the torque converter clutch apply/release tables.

I now have the transmission shifting within the ballpark of what I want for both Normal and Tow/Haul mode pulling my 3,300 pound trailer. I can refine the transmission behavior as desired in the future.

Again, my disclaimer of liability is that if you use this information, you do so at your own risk, since altering the factory settings may damage your engine or transmission.

 

[k_arnold72]

Can this only be accomplished with a laptop? If a desktop is my only computer, how can I transfer files to the vehicle?

 

[RobH]

Can this only be accomplished with a laptop? If a desktop is my only computer, how can I transfer files to the vehicle?

You can do it with a desktop which has a USB port. You'd carry the desktop out to the car and connect it to the MPVI3. The only risk is the fact that the desktop does not have an internal battery. So there might be an issue with spurious electronic currents from the desktop power supply getting on the cable to the HP Tuner MPVI3. If you have a robust UPS and could operate the desktop off of the UPS battery, that would not be a problem.

On the HP Tuners Forum on the HP Tuners website, there is a thread

Safety Tip: Please Read Me Before you Write to any PCM/ECM with your Laptop

This is Just for Safety.....write to the PCM at your own risk For maximum Safety... Never write to the pcm without guaranteed power.. Meaning plug in your laptop laptop..and double check the connection to make sure the Laptop is Charging and getting power...a lose connection could mean you...

forum.hptuners.com

where two HP guys, Scott and Bill, tell it both ways. The thread has several posts from other people.

If you don't have a robust UPS for your desktop, perhaps you have a friend with a laptop with a robust battery.

Twenty years ago my laptop gave me the "Plug in your battery charger soon." message and died before I could plug it in or finish writing the calibration file to my wife's daily driver 1995 Buick Roadmaster. Big oops.

Down to the salvage yard to buy a PCM out of a 1995 Firebird. It had the same part number as the Buick PCM. I installed the Firebird PCM in the Buick and wrote the Buick file to the Firebird PCM. It worked. Thank you, Father.

I sent the failed Buick PCM to a guy who rehabbed it for a reasonable fee. I kept it as a spare after testing it in one of our two 1995 GM sedans.

FWIW and YMMV.