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Tuner for 5.3V8 GMC Sierra

Old 09-19-2018, 09:29 AM
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Default Tuner for 5.3V8 GMC Sierra

I have a 5.3 L V8 in a 2014 GMC Sierra. The tow rating for my truck is 9000 pounds. I probably come close to 7500 to 8000 when my boat is fully loaded. At this weight I get anywhere between 8 to 9 miles per gallon when towing on the highway. Normally tow at 60 mph.

Does anyone out there have a truck and towing scenario that is similar to mine and have you bought and used a tuner to increase towing economy? What kind of gains have you seen? I would love love to see a solid 10mpg and am open to any suggestions and just trying to figure out whether or not a tuner is even worth the money.Thanks.
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Old 09-19-2018, 10:36 AM
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You could do a tuner but I don’t think you are able to change tunes on the fly like a diesel
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Old 09-19-2018, 10:54 AM
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Does it allow me to select different shift points?

I think I would get the most gain if I could just sit at the bottom RPM of the highest gear while at 60 mph.
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Old 09-19-2018, 11:30 AM
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You aren't going to see 10 MPG out of a gas motor pulling 8K at 60MPH.

The only reason I would bother tuning a 5.3 is power. Seeking economy when towing is a waste of time.
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Old 09-19-2018, 11:38 AM
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Originally Posted by autobaun70 View Post
You aren't going to see 10 MPG out of a gas motor pulling 8K at 60MPH.

The only reason I would bother tuning a 5.3 is power. Seeking economy when towing is a waste of time.
Thanks. I have plenty of power. More so looking to change shift points to get that extra couple mpg. Doesn't sound worth while at first but I do several long distance tow trips annually and I figured if I could get RPM down with new shift points a tuner would pay for itself.
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Old 09-19-2018, 11:50 AM
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Originally Posted by Snapper Smacker View Post
Thanks. I have plenty of power. More so looking to change shift points to get that extra couple mpg. Doesn't sound worth while at first but I do several long distance tow trips annually and I figured if I could get RPM down with new shift points a tuner would pay for itself.
Are you trying to hold top gear 60+ MPH? With that kind of weight, that is likely a recipe for a transmission disaster.
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Old 09-19-2018, 12:00 PM
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You are not going to gain anything with a tune under your situation. Take this from someone who spent 30 years in engine controls design/development/calibration/software.

Push in the tow-haul button and just drive it. If you want to play the game of lower RPM (higher gear), take off the tow-haul button for a while and it might grab a higher gear for a bit, but then spend a lot time downshifting and upshifting which will not be a good thing for the trans.
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Old 09-19-2018, 12:02 PM
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I'm not sure what you mean by holding top gear. It's an automatic transmission. The only input I provide to the transmission is depressing the tow mode button before I begin towing and then the gas pedal to keep the truck at 60, which is where I feel comfortable towing.

At that speed, on flat ground, the truck settles out at about 2000-2200 rpm. I'd like to get it down to 1750 or so.

Looking to see if someone has already tried to adjust shift points using a tuner and what kind of gains you obtained.
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Old 09-19-2018, 12:03 PM
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Originally Posted by ericinmich View Post
You are not going to gain anything with a tune under your situation. Take this from someone who spent 30 years in engine controls design/development/calibration/software.

Push in the tow-haul button and just drive it. If you want to play the game of lower RPM (higher gear), take off the tow-haul button for a while and it might grab a higher gear for a bit, but then spend a lot time downshifting and upshifting which will not be a good thing for the trans.
Thanks Eric.
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Old 09-19-2018, 12:28 PM
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Autobaun and Ericinmich are spot on. A tune is not going to help you. Off the shelf handheld programmers are not going to do anything to increase your fuel mileage on a regular modern gas engine regardless of what they claim. Sure they may make a few more HP but if you look at a dyno chart the gains are at the upper limits in RPM's and nothing below it. There are a few benefits to them such as calibrating the speedometer for gear and tire size changes or turning off AFM but that is it. Also trying to force the truck to stay in a higher gear is only going to put strain on the engine and transmission and could even cause damage. As said before, put the truck in tow haul mode and let it do it's thing.

Now there are exceptions. Turbo diesels and gas engines like the Ecoboost in the Ford pickups will see noticeable gains with a tune but even then I would stay away from the canned, off the shelf tunes.
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Old 09-19-2018, 12:44 PM
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Tried a Diablo tuner on my 5.3. Can tweak a few more horsepower but did nothing for fuel economy. Running a 22 gallon gas tank towing 6500 pounds is a pain. Your are running at a good speed, need to live with what you have.
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Old 09-19-2018, 03:04 PM
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All the above info is spot on. But if anyone can help........Black Bear Performance :: Custom Tuning Solutions for 96 and newer GM Vehicles
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Old 09-19-2018, 03:12 PM
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Originally Posted by Salmonbum View Post
All the above info is spot on. But if anyone can help........Black Bear Performance :: Custom Tuning Solutions for 96 and newer GM Vehicles
Sounds like tuning is not the answer. Thanks everyone.
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Old 09-19-2018, 04:08 PM
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I would disagree that a tune is worthless, I've tuned a 6.0 gm gas burner and a 5.3 as well, granted the gains weren't mind blowing but I gained 1 mpg on the 6.0 and 1.5 on the 5.3. Power wise it wasn't much but the shifting was improved. That was with a hyper tech and a jet programmer, my 14 GMC will be getting tuned by black bear performance.
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Old 09-19-2018, 04:32 PM
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I tuned my naturally aspirated ford 5.4L with a SCT livewire and custom tunes from 5Star. In terms of power and performance it was a total waste of money and I expect it would be a waste on any naturally aspirated engine. I do, however, like it for keeping an eye on my transmission fluid temps and a few other data points.
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Old 09-19-2018, 04:50 PM
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Trifecta tunes let you switch on the fly by triggering the cruise control on/off button. Have one of those on my Colorado.

Built a lot of tunes with HP tuners when I was big into the LSX racing scene.
You can gain a lot through the rpm range just not at WOT.

​​​​​​To really dial it in you need a wideband HP Tuners.
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Old 09-20-2018, 04:55 AM
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I agree with others as I have looked into this with Diablo tunes and a custom tuner, nothing that can be done specifically for towing. If you wanted higher shift points for higher RPMs, that can be done, but that's about it.

Also as as others have stated, running lower RPMs can cause issues with the trans, so not recommended. Gas engines NEED higher RPMs to make power to tow, you don't want inhibit that.
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Old 09-20-2018, 07:57 AM
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Originally Posted by Snapper Smacker View Post
I'm not sure what you mean by holding top gear. It's an automatic transmission. The only input I provide to the transmission is depressing the tow mode button before I begin towing and then the gas pedal to keep the truck at 60, which is where I feel comfortable towing.

At that speed, on flat ground, the truck settles out at about 2000-2200 rpm. I'd like to get it down to 1750 or so.

Looking to see if someone has already tried to adjust shift points using a tuner and what kind of gains you obtained.
The Tow Haul mode is keeping you at the higher rpms because you have more torque and THAT IS GOOD...

Relax let it do it's work,,,,, 10 mpg at 8000 bs.... not going to happen 8-9 mpg t 60 mph is damn good hauling that weight....
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Old 09-20-2018, 08:08 AM
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I just don't see ANY 1/2t gasser pulling 7500-8k getting much better mileage on the highway!

The wife has a 2015 Suburban LT (5.3, 6spd, 2x4, 3.08 rear, 18" wheels) pulling my 2400 BlueWave/Yam 300 to our place in FL (500miles each way) it gets 1-1.5mpg better than my 2016 Silverado CC 4x4 (5.3, 6spd, 3.42 rear, 17" wheels). Both I tow around 70mph, "tow/haul" on so it typically stays in 5th and the Sub turns maybe 150-200 Rs less? But empty that Sub gets 3-4mpg better than my Silverado as well, so the mileage diff doesn't surprise me. I swear the Sub feels "peppier & less labored" even with it's 3.08 rearend vs my Silverado!

I bought my Silverado about 3 mths before I bought the BlueWave, otherwise I would've gotten a 6.2 equipped GM truck. I'm eagerly awaiting the new "baby max" inline turbo diesel coming in the 2019 Silverado!
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Old 09-20-2018, 08:17 AM
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Prob the best way to lower the rpm would would be to go to a nu,erically lower rear end gear. If you have 3.73 maybe go to 3.42 or 3.08. And if a 4wd you would need to do the front as well
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