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I just cant believe that with all of the experiences and knowledge on this site, that I cannot get a straight answer to this problem. I am certain someone here has figured out how to correct this issue. Any help would be greatly appreciated.

I have a 2018 Denali Duramax and without thinking about it, as I have done with all of my past trucks, 1987 Blazer, 1993 Tahoe, 2000 Tahoe, 2008 GMC Duramax LTZ, changed the gearing to fit my lifted trucks and tire size, 35's, and there has never been a problem. Now, get to the 2018, and it has been a royal pain in the ass ever since I changed out the 3:73's to 4:56's. With the ECM, and TCM and wheel sensors all messed up now, I am in a quandary on how to fix it, without replacing the 4:56's back to the 3:73's.

Ever since I replaced the gearing, I have been having issues with the shifting sequence being completely off and the truck thinking its going 110mph, but in reality only going 83mph and the damn governor is kicking in and not allowing me to go any faster! In addition to that, the cruise cruise control doesn't work, and I am impeding traffic in the slow lane because I cant get out of my own way because the powerband is not right.

That being said, I have been searching for over a month now, asking diesel shops, Flying High 4WD, Desert Ratt, GM dealerships, racing shops and friends where I can get this taken care of. My latest call was to a truck computer specialist who recently told me that it is better to reprogram the ECM/TCM and have everything working correctly before adding a tuner. Any thoughts on that? Does it matter? I have heard some tuners can correct some of the problems, but the cruise control is still an issue. Who do you have to know to get this fixed? I need someone who knows truck codes and terminology who knows how to fix this issue.

To add insult to injury, I am pulling a 38' fifth wheel, and cant do that until this issue is corrected. That being said, I do have some additional questions, because I definitely need more power.
1) Does the Edge tuner actually address all of these issues/ correct these issues without reprogramming the ECM?
2) Is Edge better than Bank's in your opinion?
3) Any advise, if you have any insight on what upgrades I should look for or use pulling a fifth wheel, to get more power to the wheels/ torque?

I am prepared to put some money in the truck to make it right, and legal. I am not trying to delete everything and role coal. I want the truck to perform to its best potential, and tow as it should.

Thank you in advance for your time.
 

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2019 3500HD 4x4 Cclb, Banks Intake, AG Diesel Module
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I think the Pulsar v3 will address the tire size and shifting issue. I don't think it's possible to get cruise back though as far as I know.

You also wouldn't stack a tuner on top of an ecm/tcm tune. It might work out best for you to go through Duramax tuner and get their ecm and tcm. But that will be either a swapped ecm/tcm or they have a buy new option I think. Might would give them a call before you do anything as if it's possible they would know.
Calibrated Power, home of DuramaxTuner
 

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I just cant believe that with all of the experiences and knowledge on this site, that I cannot get a straight answer to this problem. I am certain someone here has figured out how to correct this issue. Any help would be greatly appreciated.

I have a 2018 Denali Duramax and without thinking about it, as I have done with all of my past trucks, 1987 Blazer, 1993 Tahoe, 2000 Tahoe, 2008 GMC Duramax LTZ, changed the gearing to fit my lifted trucks and tire size, 35's, and there has never been a problem. Now, get to the 2018, and it has been a royal pain in the ass ever since I changed out the 3:73's to 4:56's. With the ECM, and TCM and wheel sensors all messed up now, I am in a quandary on how to fix it, without replacing the 4:56's back to the 3:73's.

Ever since I replaced the gearing, I have been having issues with the shifting sequence being completely off and the truck thinking its going 110mph, but in reality only going 83mph and the damn governor is kicking in and not allowing me to go any faster! In addition to that, the cruise cruise control doesn't work, and I am impeding traffic in the slow lane because I cant get out of my own way because the powerband is not right.

That being said, I have been searching for over a month now, asking diesel shops, Flying High 4WD, Desert Ratt, GM dealerships, racing shops and friends where I can get this taken care of. My latest call was to a truck computer specialist who recently told me that it is better to reprogram the ECM/TCM and have everything working correctly before adding a tuner. Any thoughts on that? Does it matter? I have heard some tuners can correct some of the problems, but the cruise control is still an issue. Who do you have to know to get this fixed? I need someone who knows truck codes and terminology who knows how to fix this issue.

To add insult to injury, I am pulling a 38' fifth wheel, and cant do that until this issue is corrected. That being said, I do have some additional questions, because I definitely need more power.
1) Does the Edge tuner actually address all of these issues/ correct these issues without reprogramming the ECM?
2) Is Edge better than Bank's in your opinion?
3) Any advise, if you have any insight on what upgrades I should look for or use pulling a fifth wheel, to get more power to the wheels/ torque?

I am prepared to put some money in the truck to make it right, and legal. I am not trying to delete everything and role coal. I want the truck to perform to its best potential, and tow as it should.

Thank you in advance for your time.
I echo @FreedomOne's sentiments regarding the "stacking" of an ECM/TCM tune with an inline tuner; I don't see how that would make any sense. At best it would be redundant and at worst it would create some kind of tuning/programming conflict.

The 2017+ trucks require a complete ECM swap for any kind of tuning (back off, Big Brother -- we're talking emissions-compliant tuning for the sole purpose of regearing or changing tire diameters). It's several thousand dollars and I'm not sure the regearing is something available "off-the-shelf" or if you'd have to pay for custom work. If I had to hazard a guess I'd suspect you're getting close to five-figures territory in terms of cost; that's pretty much a made-up number and hopefully someone else can chime in with a more precise estimate (but I wouldn't hold my breath, if I were you).

This thread was posted a while back by a guy who has since stopped participating on this forum but it goes over the same issues you're dealing with. I guess the bottom line is that there's no readily available solution and if you want reasonable behavior from your truck you're going to have to revert to the 3.73 gears.

Good luck and let us know what you wind up doing.

Edit: Maybe I was being a bit too cryptic with the above. Specifically, I don't think any inline tuners or "plug and play" solutions are going to restore cruise control (for me, cruise is an absolute necessity for highway towing, especially in the mountains). I believe the speedometer output can be corrected, though, but I don't know about the electronic speed governor.
 

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I certainly don't have your answer but got to wondering if your answer lies in the 4500/5500 realm. Those heavier trucks run lower geared rearends with virtually the same drivetrain otherwise, I believe.
 

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The medium duty trucks usually come with 4:30 gearsets. Trans is one of several available heavy duty Allisons. Mine happens to be a RDS 1700. It does have a governor set at 74. This has to do with the 4:30's although IMO thats plenty fast enough for a truck. Looked into some minor mods for the engine but none available for the L5D engines but I'm happy with what I have anyway.
 
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The medium duty trucks usually come with 4:30 gearsets. Trans is one of several available heavy duty Allisons. Mine happens to be a RDS 1700. It does have a governor set at 74. This has to do with the 4:30's although IMO thats plenty fast enough for a truck. Looked into some minor mods for the engine but none available for the L5D engines but I'm happy with what I have anyway.
Sounds like more differences than I thought.
 

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2017 GMC Denali 2500HD, 3.5" Rough Country Lift, 305/55R20 Yokohama Geolandar A/T
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OP, I would give a call to PPEI or DuramaxTuner and ask them what they know about regearing these trucks and how it relates to programming the ECM.
 

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@More Cow Bell ,
What you're trying to do isn't simple, that's why you haven't found much information. The computers in these trucks are fully locked down. To do it right, you either need to get your computer unlocked, or purchase an unlocked computer.
The issue is that the wheel speed sensors go to the main computer. The main speed sensor on the transfer case goes to the transmission computer first, then the main computer reads the data from the transmission computer.
The answers you seek are in the first post of this thread...
Good luck

Also, here is another thread with info

And another...
 

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On one of the forums one guy modded his l5d into a L5p.
Why? you have to replace turbo and ECM neither of which is cheap and for 100 hp and 200 # torque. The truck weighs 11K and moves just fine with what its got already. Guy must be like ones wanting to do away with a governor set at 90+
 
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By any chance would uses a turner software like efilive and go in a change the programming would that fix the problem? Another though is could you move the wheel sensor in a position to make it think it’s in the same location? Like moving it closer or further away from the center of the hub? Sorry never looked at the wheel sensors in that truck so not clue if it’s even possible. But is there away you can make the sensor think it’s back it’s to stock or is there a programmable wheel sensor?
 

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The sensor is actually in the hub with a trigger ring. It has to be shimmed for the correct clearance and unless you replaced the hub without checking that clearance, it shouldn't' affect anything. UTEngineer ran into all of this and slowly worked thru most if not all the problems. Go look his post up-- I think it is the ones Viper is referencing.
 
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UTEngineer ran into all of this and slowly worked thru most if not all the problems. Go look his post up-- I think it is the ones Viper is referencing.
^^This!
 

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What @Mc4life27 is referencing is not an option. The L5P factory computers have locked bootloaders that look for an encrypted signed key in the software to even boot up. Please stop with the speculation and what ifs to avoid confusion. The old days of just plugging in a little programmer and making changes are gone. In order to make changes you need to either send your computer to be unlocked, or buy a new unlocked one.
Modifying the wheel speed sensors mechanically will not solve the issue either.
 

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I reread Mclife's post and realized that he thinks the wheel speed sensors are what determines vehicle speed. Sorry for my confusion. The wheel sensors are for the anti-lock and traction control systems.
 
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I reread Mclife's post and realized that he thinks the wheel speed sensors are what determines vehicle speed. Sorry for my confusion. The wheel sensors are for the anti-lock and traction control systems.
Sorry I was not aware on how the wheel sensors factor in. I knew it wasn’t for the trucks speed. I was thinking more like a bicycle computer were there is a
Magnet in the wheel and a pick up mounted to the forks. On some of those of
You either raised the pick up and magnet up
Or
Down the fork it would think it’s on a different size wheel then what it is. I was thinking if it picked up it’s info as it went around going down the road. Didn’t know it was more of a shimmed in and out from the center to the outer edge of the truck. I figured if someone was able to hack the computer you could tell it what it needs to know and sure sounds simple. But I have heard that some suspension companies were having issues then the hacking part maybe out of the question at the current time. If the computers could be hacked that way then thoses companies would have just done that since they have the money and resources to do so. But currently is the computer hackable to program the wheel sensor currently?
 

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Ok sorry if I’m adding to confusion but I learn quick and remember things so I may o ly
Ask the dumb questions once. Since it’s messing with the tranny and shift points, I was watching a YouTube video of a company that makes adapters for alisons that’s all the do so you can run a Cummins or a power stroke or any motor really and they had all the parts and even a full stand alone computer system They also have a stand alone system that would plug into a duramax and Alison truck and what it would do is tell the o
Computer everything is good to go but the stand alone would be controlling the Allison on its own and they claimed it worked better then the gm computers. I will try and find what the company was. I find it hard to believe that it’s impossible to swap the gears out and have the truck function properly. If they did that wouldn’t that be going against the law that has to do with aftermarket products and factory warranty. I though there was something in place were a car manufacturer couldn’t make things so that the truck could not be serviced and parts replaced by using aftermarket parts? It a way say a company made an oil filter for a truck and you had to use their filter and their filter only or else it would not work? I’m sorry if I’m thinking ass backwards about it but I’m also trying to think of other ways around it and maybe can help remind someone (who is more knowledgeable) of something else? Sorry but after the 29 bit lan systems I don’t know all that much about the trucks since i no longer get work at a company that does stuff like that. Also I’m trying to think of was that we’re used back in the day to get around stuff just maybe in a different configurations. If I’m way off I will just shut up and just follow and not
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I saw on another post that hypertec makes an inline adaptor to correct for tire sizes and maybe gear changes.
Did you go back and read all of UTengineer's post on the exact things you are doing and asking about?
 

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A delete tuner or emissions compliant tuner can compensate for tire size and make speed adjustments so everything runs accurately on the speedometer.

I understand regearing a vehicle to improve low end performance. But to the OP you are driving a diesel truck with 35s, this should never require to be regeared. These diesel trucks do not have to be regeared unless you are running 37s or bigger and even then the duramax engine and Allison transmission are built well enough to handle bigger tires. You should have just bought customs tunes for ecm and flashed your truck.

My advice put the 3.73 gears back in and if it doesn’t fix the truck, take it to dealership to reflash ECM and once it is working as it should order tunes if you are seeking more power. If not just leave the truck alone it has plenty of power to pull a trailer at 80mph.
 

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I just cant believe that with all of the experiences and knowledge on this site, that I cannot get a straight answer to this problem. I am certain someone here has figured out how to correct this issue. Any help would be greatly appreciated.

I have a 2018 Denali Duramax and without thinking about it, as I have done with all of my past trucks, 1987 Blazer, 1993 Tahoe, 2000 Tahoe, 2008 GMC Duramax LTZ, changed the gearing to fit my lifted trucks and tire size, 35's, and there has never been a problem. Now, get to the 2018, and it has been a royal pain in the ass ever since I changed out the 3:73's to 4:56's. With the ECM, and TCM and wheel sensors all messed up now, I am in a quandary on how to fix it, without replacing the 4:56's back to the 3:73's.

Ever since I replaced the gearing, I have been having issues with the shifting sequence being completely off and the truck thinking its going 110mph, but in reality only going 83mph and the damn governor is kicking in and not allowing me to go any faster! In addition to that, the cruise cruise control doesn't work, and I am impeding traffic in the slow lane because I cant get out of my own way because the powerband is not right.

That being said, I have been searching for over a month now, asking diesel shops, Flying High 4WD, Desert Ratt, GM dealerships, racing shops and friends where I can get this taken care of. My latest call was to a truck computer specialist who recently told me that it is better to reprogram the ECM/TCM and have everything working correctly before adding a tuner. Any thoughts on that? Does it matter? I have heard some tuners can correct some of the problems, but the cruise control is still an issue. Who do you have to know to get this fixed? I need someone who knows truck codes and terminology who knows how to fix this issue.

To add insult to injury, I am pulling a 38' fifth wheel, and cant do that until this issue is corrected. That being said, I do have some additional questions, because I definitely need more power.
1) Does the Edge tuner actually address all of these issues/ correct these issues without reprogramming the ECM?
2) Is Edge better than Bank's in your opinion?
3) Any advise, if you have any insight on what upgrades I should look for or use pulling a fifth wheel, to get more power to the wheels/ torque?

I am prepared to put some money in the truck to make it right, and legal. I am not trying to delete everything and role coal. I want the truck to perform to its best potential, and tow as it should.

Thank you in advance for your time.
You don't say in your post where you're at, but the guys at Leadfoot Diesel Performance in Madison, Ga., are about the best I've ever seen. Give them a call, or hit them up on Instagram.
 
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