2018 GMC Denali swapping to 4.11 Gearing

[DHeinze]

As not to start another string on gearing swaps.... 

I have a 18 sierra Denali 1500 6.2 with 3.42 gears. We pull right up to the max for the truck with our travel trailer and spending a lot of time in Colorado. I have no complaints with the 3.42 gearing until we head up hill 6% grade, there is way to much loss in speed and gear seeking. 

We have found a local shop that will put in the 4.11 gears, but does not do programming. The dealership warranty or not doesn't want to modify it, for the 4.11. Diablo after 45 minutes on the phone told me, yes their T2EX or the I3 would program the truck for the gearing. My problem is I know nothing about programming or do I care to learn at this point. The local tuner shops wont touch it unless it is their brand and they don't have the unlock for the tranny for the 18 models.

So... Anyone in Texas up for some cold beer and some lessons with a Diablo??

[KARNUT]

As not to start another string on gearing swaps.... 
I have a 18 sierra Denali 1500 6.2 with 3.42 gears. We pull right up to the max for the truck with our travel trailer and spending a lot of time in Colorado. I have no complaints with the 3.42 gearing until we head up hill 6% grade, there is way to much loss in speed and gear seeking. 
We have found a local shop that will put in the 4.11 gears, but does not do programming. The dealership warranty or not doesn't want to modify it, for the 4.11. Diablo after 45 minutes on the phone told me, yes their T2EX or the I3 would program the truck for the gearing. My problem is I know nothing about programming or do I care to learn at this point. The local tuner shops wont touch it unless it is their brand and they don't have the unlock for the tranny for the 18 models.
So... Anyone in Texas up for some cold beer and some lessons with a Diablo??

It’s easy and just button pushing. Give a call to Pyle brothers see if they’ll help you out. I haven’t used them in awhile, I’m sure they’re still around. But otherwise hand held tunes are very easy to navigate.


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[Denali_King]

If it's a Denali it has a 3.23 not a 3.42.  The 3.42 is only available in the max tow package with the 6.2l.  That's a big change from 3.23 to 4.11!  Where are you at in Texas?   Houston house of power can get you squared away and tune both engine and trans as well.

[DHeinze]

Actually the truck came with the Denali ultimate package which up graded the gearing added the brake controller , fancy running boards, and 22"rims and gave the consumer and the salesman that false sense of NHT.... the travel trailer Max's out with us in the truck at the 9100 the truck is rated at. Just do not appreciate the capability on slopes in the mountains. Honestly we drive to Albuquerque or OKC every weekend and have seen unburdened fuel mileage in the upper 20's with the Ecotech.. hoping the 8 speed tranny keeps that somewhere close when done. I did look up Pyle I'm Baytown and are on the lost to call tomorrow..

[DHeinze]

We are in Amarillo. Sounding like a long weekend south might be the answer. Diablo told me there customer support is second to none.... just worried me if I make a mistake and Princess has the walk to work for a couple of days....?

[300 Blackout]

I purchased an AutoAnything TruXP xTune+ just to update my gear and tire size. Its $200. It is a rebranded SuperChips Tuner. Exact same thing, I even updated mine on SuperChips website.

Back on topic. The process goes like this. Plug the unit into the OBD2 port and follow the on screen prompts. The first thing the tuner does is create a backup of your stock tune so you can always revert back to stock.

Once that is complete, you choose from a menu of what you would like to do. I chose to do the stock tune with modifications in order to update tire size and gears without messing with the other stock settings.

You go through the menus to change the settings you want. Once you are happy with what you have chosen, you confirm you would like to upload your tune to the truck. You click start and let the tuner do its thing. The trucks electronics cycle as it uploads different settings and once it’s complete it lets you know. If you have any problems whatsoever, just reload the stock tune and start over. As long as you don’t unplug it or your battery while it’s loading a tune, I think you’re going to be just fine.

I have read nothing but great things about Diablo. I’m sure their interface is equally user friendly and likely a more capable system. If you used a phone or computer to post to the forum you have plenty of technical knowledge to run this type of tuner.

[pewterliftedz]

Look in your glove box and see if you have RPO code GU6 (3.42) or GU5 (3.23).  I'm pretty sure that you have a 3.23 gear set in your truck, because that was the only gear available to 6.2 Denali's.

[Nitrousbird]

Your truck has 3.23 gears.  I just went on the GMC site and built a Denali Ultimate with the 6.2L.  The only way to get 3.42's is to downgrade to a 5.3 motor in a Denali.

 

The ONLY way to get 3.42's in a 6.2L motor is to get the max trailering package, which isn't available on the Denali.  I wanted that package on a SLT but there were zero for sale on my multi-state search (including where I bought mine, which had over 800 '18 Sierra's in stock).

[Denali_King]

I have a Denali ultimate as well.  It's has 3.23 gears.  I tried ordering 1 with 3.42.  Not possible. 

[DHeinze]

On 10/31/2018 at 2:52 AM, Nitrousbird said:

Your truck has 3.23 gears.  I just went on the GMC site and built a Denali Ultimate with the 6.2L.  The only way to get 3.42's is to downgrade to a 5.3 motor in a Denali.

 

The ONLY way to get 3.42's in a 6.2L motor is to get the max trailering package, which isn't available on the Denali.  I wanted that package on a SLT but there were zero for sale on my multi-state search (including where I bought mine, which had over 800 '18 Sierra's in stock).

I stand corrected. 3.23 gearing currently. It changed on the 5.3 delete. Regardless with in a few weeks it will be 4.11. I am truly curious about what the gas mileage will be. I have read that the truck stays in 4V mode more on the highway and in town.

[DHeinze]

On 10/30/2018 at 9:41 PM, 300 Blackout said:

I purchased an AutoAnything TruXP xTune+ just to update my gear and tire size. Its $200. It is a rebranded SuperChips Tuner. Exact same thing, I even updated mine on SuperChips website.

Back on topic. The process goes like this. Plug the unit into the OBD2 port and follow the on screen prompts. The first thing the tuner does is create a backup of your stock tune so you can always revert back to stock.

Once that is complete, you choose from a menu of what you would like to do. I chose to do the stock tune with modifications in order to update tire size and gears without messing with the other stock settings.

You go through the menus to change the settings you want. Once you are happy with what you have chosen, you confirm you would like to upload your tune to the truck. You click start and let the tuner do its thing. The trucks electronics cycle as it uploads different settings and once it’s complete it lets you know. If you have any problems whatsoever, just reload the stock tune and start over. As long as you don’t unplug it or your battery while it’s loading a tune, I think you’re going to be just fine.

I have read nothing but great things about Diablo. I’m sure their interface is equally user friendly and likely a more capable system. If you used a phone or computer to post to the forum you have plenty of technical knowledge to run this type of tuner.

Let me give you my address! Haha.. very good info. I will have the programmer before the gears go in, so it sounds like I can play a bit and find what I need before its needed. 

[300 Blackout]

I stand corrected. 3.23 gearing currently. It changed on the 5.3 delete. Regardless with in a few weeks it will be 4.11. I am truly curious about what the gas mileage will be. I have read that the truck stays in 4V mode more on the highway and in town.

I’ve got 4.56 and a 6 speed trans and it stays in V4 a lot. I imagine with your 8 speed trans the benefit will be even greater. Make sure that you follow the correct break in procedure for the gears. You don’t want to overheat your fluid and kill your gears. It can and does happen. After 500 miles on the new gears I changed my differential oil as required by Yukon’s warranty and couldn’t believe how dirty it was. You definitely want to change the fluid to flush out all the metal shavings and crap that accumulates from the break in process. Good luck! Once your gears are broken in, turn off traction control, press the pedal to the floor and you’ll think you put a supercharger on your truck. It’s that good.

[DHeinze]

3 minutes ago, 300 Blackout said:

2 hours ago, DHeinze said:

I stand corrected. 3.23 gearing currently. It changed on the 5.3 delete. Regardless with in a few weeks it will be 4.11. I am truly curious about what the gas mileage will be. I have read that the truck stays in 4V mode more on the highway and in town.

I’ve got 4.56 and a 6 speed trans and it stays in V4 a lot. I imagine with your 8 speed trans the benefit will be even greater. Make sure that you follow the correct break in procedure for the gears. You don’t want to overheat your fluid and kill your gears. It can and does happen. After 500 miles on the new gears I changed my differential oil as required by Yukon’s warranty and couldn’t believe how dirty it was. You definitely want to change the fluid to flush out all the metal shavings and crap that accumulates from the break in process. Good luck! Once your gears are broken in, turn off traction control, press the pedal to the floor and you’ll think you put a supercharger on your truck. It’s that good.

My wife drives it as a daily grocery getter and I'm only looking to pull the trailer on grades better but.... there are times when a little **** needs a lesson.....?

[300 Blackout]

My wife drives it as a daily grocery getter and I'm only looking to pull the trailer on grades better but.... there are times when a little **** needs a lesson.....[emoji41]

I drove like a turtle before my gears. I don’t speed or drive like an ass. When I put my gears in it was for an all around longevity upgrade (less strain on drivetrain, trans, etc..), gas mileage and improved responsiveness in city driving. After my gears, well, sometimes it’s just fun to be pushed back in my seat a little and know the power is there if I need it.

Regarding your wife driving it, here’s a little story. When I got my Vette, the first person to drive it other than me was a friend’s wife. I went to his house to let him drive it and he insisted on her driving it first. I didn’t really understand why he was so insistent until we started driving. She chirped the wheels though third and to this day can shift faster than anyone I know. He said he never knew until one day he had a couple too many pops when they went out so she drove his cobra home while he rode shotgun. I think after that ride might be when he realized he was gonna marry her[emoji23]. If the eggs are broken when your wife gets home from the grocery store, well, she might have a little lead foot you never knew about.

[DHeinze]

35 minutes ago, 300 Blackout said:

I drove like a turtle before my gears. I don’t speed or drive like an ass. When I put my gears in it was for an all around longevity upgrade (less strain on drivetrain, trans, etc..), gas mileage and improved responsiveness in city driving. After my gears, well, sometimes it’s just fun to be pushed back in my seat a little and know the power is there if I need it.

Regarding your wife driving it, here’s a little story. When I got my Vette, the first person to drive it other than me was a friend’s wife. I went to his house to let him drive it and he insisted on her driving it first. I didn’t really understand why he was so insistent until we started driving. She chirped the wheels though third and to this day can shift faster than anyone I know. He said he never knew until one day he had a couple too many pops when they went out so she drove his cobra home while he rode shotgun. I think after that ride might be when he realized he was gonna marry her. If the eggs are broken when your wife gets home from the grocery store, well, she might have a little lead foot you never knew about.

Funny thing. This is my second wife. The first was conservative did well raising the kids. The second one a little crazy and doesn't want kids..... she graduates college this fall.... I may be in for a big surprise.....