'17 - '18 "Tuner" advice???

Jacoby · August 12, 2019

They’re probably identical in function. I’m just cheap and look for the cheaper option. Either will do the job

Racindave · August 12, 2019

On 8/9/2019 at 5:29 PM, b00001 said:

I have searched and read many of the 70 page thread on Tuners. Not finding what I am looking for pertaining to my 2018 w/ 8 speed. Surely many have been through what I am going through now. Looking for a good path to follow.

I have a 2018 Sierra SLT, 5.3 w/ 8 speed that I have installed Corsa Sport cat back exhaust as well as upped my tire size from basically a 32" to a 33" tire (went from 275/55/20 to 275/60/20).

I plan on doing the OEM airbox mod + install high flow air filter such as K&N or the dry blue filter.

My "problem" started just after I installed the new tires a few days ago. It seems am feeling the weight of the new tires as well as the increased size of the tires affecting how the truck is driving. I have the 8sp trans and before the tires, it was actually not too bad. Now with the new tires, I can feel that sluggish shifting, as well as the trans trying to shift into the next highest gear way too soon. I have heard that the trans is reading the old tire size = speed, so the shift points will be slightly off??? I understand there is no option for transmission tuning.

My question is, what would be the best way to get my truck back to feeling GOOD again while keeping budget in mind? (Just lost my job) What would be my least expensive way to get my truck dialed in? Do I need a full "tune" or would something like the $199 Superchips tuner suffice? That would allow me to turn off DOD as well as reprogram for the larger tires. I think I have about another year of warranty left that I would like to keep in good standing if possible.

Thank you all very much in advance!!!

So going to a 275/60/20 messes with transmission that much? Have any other people on here experienced this? Going up in size was my next upgrade....

b00001 · August 12, 2019

Just now, Racindave said:

So going to a 275/60/20 messes with transmission that much? Have any other people on here experienced this? Going up in size was my next upgrade....

Yes, I have read a few posts of same happening to others. Maybe some feel it more than others? For me, it is night and day difference. My truck is "off". I have swapped tire sizes on Jeep Grand Cherokees a number of times, never going much more than a size or 2 up and never felt any difference in trans shifting. Maybe with all the new electronics they have tightened up their shift points/algorithms?

Racindave · August 12, 2019

1 minute ago, b00001 said:

Yes, I have read a few posts of same happening to others. Maybe some feel it more than others? For me, it is night and day difference. My truck is "off". I have swapped tire sizes on Jeep Grand Cherokees a number of times, never going much more than a size or 2 up and never felt any difference in trans shifting. Maybe with all the new electronics they have tightened up their shift points/algorithms?

Man that’s disappointing....

b00001 · August 12, 2019

I came across the TruXP Xtune Plus Performance Tuner

Supposedly it will re-calibrate tire size, Disable DoD/AFM, Adjust Speed/Rev Limiter, read diagnostic codes.... $199 I have found a couple forum members who say they have used this on their 2017 and 2018 model trucks. I may give them a call because on the website it states that the item is not compatible for 2018.

Jacoby · August 12, 2019

It will do all that through a tune. You said you wanted to wait on a tune. If you’re going to tune the truck I suggest you stick with Lew. Bite the bullet and pay the fee. You won’t be disappointed

pewterliftedz · August 14, 2019

On 8/12/2019 at 6:02 AM, Jacoby said:

Forgot about the Range. That will get the afm turned off. The Hypertech isn’t the only option for tire size adjustment. Rough Country has a programmer that’s quite a bit cheaper.

Nice, I didn't realize they had a cheaper option.

SILVER SLED · August 15, 2019

How far off is your speedometer? I put 275/60-20s on my truck and according to gps, I’m going 60.7 mph when my speedo is reading 60, so I didn’t mess with recalibrating speedometer.

b00001 · August 15, 2019

13 hours ago, SILVER SLED said:

How far off is your speedometer? I put 275/60-20s on my truck and according to gps, I’m going 60.7 mph when my speedo is reading 60, so I didn’t mess with recalibrating speedometer.

That sounds about right. The speedometer being off doesn't bother me. It is the transmission shift points that seem to be way off now, that is my issue.

SILVER SLED · August 15, 2019

4 hours ago, b00001 said:

That sounds about right. The speedometer being off doesn't bother me. It is the transmission shift points that seem to be way off now, that is my issue.

That seems odd that the transmission shifting that differently with hardly any diff in wheel speed sensor speed. Mine shifted the same after the larger tires.

b00001 · August 15, 2019

4 hours ago, SILVER SLED said:

That seems odd that the transmission shifting that differently with hardly any diff in wheel speed sensor speed. Mine shifted the same after the larger tires.

I donno???? Mine was night and day different after installing next size up tire. I think stock was 29.75" and went to 33".

We'll see if adjusting the tire size brings the shifting back to somewhat normal.

SILVER SLED · August 16, 2019

16 hours ago, b00001 said:

I donno???? Mine was night and day different after installing next size up tire. I think stock was 29.75" and went to 33".

We'll see if adjusting the tire size brings the shifting back to somewhat normal.

Generally a 275/55-20 is 31.9" tall.

Yondu · September 1, 2019

I went from 31.6 to 33 and my 6 speed shifts differently, but mostly better. Hardly ever get a downshift clunk that I got before.

Pearl2017 · September 2, 2019

Its not just the tire size but also the weight difference. Larger heavier tires require more torque and the stock trans is calibrated for stock tires.IMO It will help if you went up 5% in tire size and 5% in weight to also calibrate your tire "Rotations per mile" down by similar value. Wont the dealer also adjust it for you? ...they do sell lifted oversize tire customs with warranty.