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Hello,

I got a question about re gearing from 3.42 to 4.11. is it necessary to get the tune/ speedometer  calibrated ?

My truck 2018 Z71 5.3 6speed 3.42 gears. I got a 8" lift with 35 /12.5/20. The actual tire measures 34.5 x 13.25.

I don't want to void the factory warranty by plugging in a tuner if possible but I would hate to cause more damage by not tuning also.

Thanks

 

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Yes you will.

 

Hypertech makes a speedo caliber that only adjusts for tire and/or gear swaps. This is what the Chevy stealership that I had do some of the work on my truck use for the new ones they lift/level and wheel/tire. This is what I used on mine when I did wheels/tires before I got it tuned. It will show up,on the ecm hit counter if they go looking for it but since all it does is correct the speedo the only warranty they could say your possibly voiding is the same you would be with gears, lift and wheels/tires anyway IMO.

 

link to Hypertech 

http://www.hypertech-inc.com/SpeedometerCalibrator.aspx

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6 hours ago, wforrest08 said:

Yes you will.

 

Hypertech makes a speedo caliber that only adjusts for tire and/or gear swaps. This is what the Chevy stealership that I had do some of the work on my truck use for the new ones they lift/level and wheel/tire. This is what I used on mine when I did wheels/tires before I got it tuned. It will show up,on the ecm hit counter if they go looking for it but since all it does is correct the speedo the only warranty they could say your possibly voiding is the same you would be with gears, lift and wheels/tires anyway IMO.

 

link to Hypertech 

http://www.hypertech-inc.com/SpeedometerCalibrator.aspx

Hey thanks for the reply!!!

And the reason for the calibration is because of the anti lock breaks / stability track or traction control ? My shop says that it might throw codes if I don't do the calibration for gear ratio. 

 Ok that would make sense. Having only the option to calibrate tire size and gear ratio vs being able to adjust for performance...

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If you don’t tell the computer you changed ratios you’ll get a check engine light. Since you’re gonna go in and change things to get the speedo right then you might as well tune it. 8” lift on 35’s even with gears your truck is still a dog and is gonna he shifting poorly. 

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You’re going to love it.

I have a 6” with 35’s and I re-geared from 3.42 to 4.10s. The truck was meh with stock gears but then I went 4.10s and it felt like I was driving my truck stock again with no lift.

I get about 14.5 to 15mpg period everywhere. I can get up close to 18s on long rides (I mean like 2 hours one way).

I got my tune from Diablew and it’s 93 octane. I figure since I lifted it, threw heavy tires on, and plan to keep it long term I might as well run better fuel.

Lew tune in 93 will adjust some shifts, hold couple gears tad longer, up timing little, increase throttle response (pedal) and disable AFM.

However, big reason I changed gears was to help transmission out with turning the tires.

Enjoy mate!


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If you went through the effort for a large lift and tires why not finish the job and re-gear and tune? Your speedo and shift points will be quite a bit off with that tire size. Killing your truck leaving it that way. Very hard on the trans and gives crappy driveability.

I would def go the largest gear your carriers support and get it fully tuned. Plus leaving it as is does not work too well as a tow set up and your about as hard on the truck as you can be asking it to give/break something. These trucks with large tires need recalibration. Then increase the rotating mass and reduced aero with the lift you need to compensate for all that, otherwise dog city when towing, (or driving at all for that matter) plus your hammering it depending on how much weight your towing.  

 

Just do it right and you'll be happier. Truck looks good though.                                                                                              

 

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26 minutes ago, kennerz said:

If you went through the effort for a large lift and tires why not finish the job and re-gear and tune? Your speedo and shift points will be quite a bit off with that tire size. Killing your truck leaving it that way. Very hard on the trans and gives crappy driveability.

I would def go the largest gear your carriers support and get it fully tuned. Plus leaving it as is does not work too well as a tow set up and your about as hard on the truck as you can be asking it to give/break something. These trucks with large tires need recalibration. Then increase the rotating mass and reduced aero with the lift you need to compensate for all that, otherwise dog city when towing, (or driving at all for that matter) plus your hammering it depending on how much weight your towing.  

 

Just do it right and you'll be happier. Truck looks good though.                                                                                              

 

I'm getting the gears changed, I am asking if it is necessary to do the tune and or calibration because of the warranty . 

And should I go bigger on my gears? They do offer a 4.56 but I was told my 1st gear would basically be useless and I would have higher RPM at 75-80mph around 2300 vs 2000.

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Is it necessary no. You’ll just have a check engine light on all the time. as soon as you swap gears your drivetrain warranty is gone. So you might as well calibrate the ecm for the gear swap to get rid of the check engine light. Since you’re doing that you might as well tune it and get some more performance out of the thing. Gears will wake it up for sure but without a tune you’re still leaving a lot of performance on the table

 

whos telling you first gear will be useless and what do you intend to use first gear by itself for?  Sure your rpms will go up but so will your gas mileage. 300 rpm is nothing. As said above with your setup I’d go as big as you can. I wouldn’t go less than 4.56. All a bigger gear is doing is getting you back to what your truck would be stock. 8” lift on 35’s means you’re rolling around in what a stock truck would feel like with 3.08s. A 3.73 gear would get you back to 3.42. A 4.10 gear would get you to 3.73. A 4.56 gear would get you to 4.10.  You want a big gear to move all that added weight efficiently and easier. 

 

Im similar setup as yours. I have a 7” lift on 35s and I’m getting 4.56s put in on the 27th. I can’t wait. 

F827-AEC1-5993-4-A84-B9-D8-8296197-C1-AB

 

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4.56 is far from useless... whoever gave that info sounds like the useless one haha.  I have been running 4.56s in my 2017 Sierra with 295/60/20s for over a year now and it's by far the best mod I have done to the truck.  If I would have gone larger diameter than what I am I would have gone to 4.88.  

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3 minutes ago, SierraHD17 said:

4.56 is far from useless... whoever gave that info sounds like the useless one haha.  I have been running 4.56s in my 2017 Sierra with 295/60/20s for over a year now and it's by far the best mod I have done to the truck.  If I would have gone larger diameter than what I am I would have gone to 4.88.  

Do you have the same 5.3 with 6speed?

I'm not dead set on any one ratio. But I was told by a reputable shop that with 4.56 gears I would be shifting gears before I left the crosswalk.  At what speed is your 1st gear shifting and what's your [email protected] because nobody's driving 70 mph unless I'm pulling my trailer.

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Good thread ...   my next mod is gears as well..   I'm already tuned so easy adjustment when regear takes place ...  

  I'm trying to decide between 4.10 vs 4.56

 

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Do you have the same 5.3 with 6speed?
I'm not dead set on any one ratio. But I was told by a reputable shop that with 4.56 gears I would be shifting gears before I left the crosswalk.  At what speed is your 1st gear shifting and what's your [email protected] because nobody's driving 70 mph unless I'm pulling my trailer.


I have 4.10s and 5.3/6.

I run around 1800-2k at 75-80.

Last time I took it to Orlando doing 75 average I was getting 18mpg.


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6th gear on 6L80e ratio is .67 

So with ..  4.56 gears , 35 inch tires 

75 mph = 2200 rpm. 

4.11 gears = 1983 rpm 

3.73 gr =  1799

3.42 gr = 1650 

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56 minutes ago, FlipZ71 said:

Good thread ...   my next mod is gears as well..   I'm already tuned so easy adjustment when regear takes place ...  

  I'm trying to decide between 4.10 vs 4.56

 

4.10's will be tits for you

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1 hour ago, Carversonline said:

Do you have the same 5.3 with 6speed?

I'm not dead set on any one ratio. But I was told by a reputable shop that with 4.56 gears I would be shifting gears before I left the crosswalk.  At what speed is your 1st gear shifting and what's your [email protected] because nobody's driving 70 mph unless I'm pulling my trailer.

I have the same ratio 6 speed trans or I wouldn't reply.  Engine is irrelevant.  

 

I don't pay attention to what speed it shifts out of first at.. don't care lol.  The truck drives great.  70 mph with tires an inch and a half smaller than an actual 35 is 2100 rpm.  I don't drive 80 mph anywhere... speed limit is never that high.

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