2014, 5.3L, Silverado tire size change

[truethinker]

My father in law has a 2014 High Country Silverado, 5.3, 4x4. He went from 265/65/18 to 265/70/18 and I'd like to correct his speedo for him. I've corrected a number of speedometers on LS1B vehicles but never something this new. I don't want any issues partly for the obvious and partly because we're in Maine and he will have a 12 hour drive home at the end of the week.

Just looking for any clarification on this. Does it work the same as the older vehicles? Simply use the speedo correction tool and apply? Will this adjust shift points or just the speedometer?

Thanks!

[Taz]

I know that you are just trying to help your father-in-law, but by flashing the ECM you will void his GM warranty.

I would recommend addressing this through your GM dealer, or finding a tuner that has an MDI and SPS / TIS subscription – and having them deal with the GM Help Desk (not always helpful) to see if they will release an updated calibration for the vehicle. Here is the caveat, the tire size (diameter) will have to correspond to an OEM tire size offered for that vehicle in 2014. The tire does not need to be the exact same p-metric designation, just the same (or very close to the same) diameter.

[Taz]

Sorry, busy day ... just did the math. You are only looking at about a 3.5% error. If the speedometer indicated 48.25 MPH, the true speed would be 50 MPH. May not be worth the bother to correct - the odometer will also increment 3.5% slower than actual.

[truethinker]

Thanks Taz! I should have included this information as it was my first question but he has no warranty left. He's at 70k miles.

[truethinker]

From the sound of things he will want a tune at some point also so it wouldn't be a wasted license. I would probably send out to Blackbear for the tune ad I haven't done anything this new.

Either way, with no warranty and probably doing a tune at some point does this change the opinion of correcting the speedometer now?

[Taz]

If the vehicle is no longer under warranty then have at !

Tuning the transmission will make a significant improvement in the driving experience - if your father-in-law is an old school car guy. One of my best customers is in his 70s, and likes the transmission shifts to be bordering on harsh in all of his custom vehicles - he makes me laugh.

[truethinker]

Definitely not an old school car guy. Neither old school nor a car guy. More of a business man who like his snow mobiles, boats and vacationing in rural Maine if that gives you an image.

I wouldn't do anything that drastically changes the feel of the truck. Just "improve" it's function.

Right now though just tire size if anything. Would I go about that with the usual speedo correction tool used for the genIII LS1B stuff or are there TCM corrections too?

[Taz]

Too funny – perhaps no tuning at all then.

Regarding the Speedometer …

I rarely work with an OEM vehicle, so I am not certain which of several options would work for you. You also have an EBCM (ABS) on the CanBus network to consider – and not upset.

First, confirm with a GPS device that the Speedometer display is accurate or inaccurate – there is often a small compensation factor built in. If inaccurate, calculate the percentage of error (likely 3.5%).

If the Speedometer reads slow, then you will decrease the values below (H0105 and / or H0136) by the percentage error. If the Speedometer reads fast, then you will increase the values below (H0105 and / or H0136) by the percentage error. In your case it will either be accurate (or very close), or a little slow.

ECM – adjust H0105 (ECM pulses / mile)

TCM – adjust H0136 (Tire revs / mile)

You may only need to adjust one of these, or you may need to adjust both of these – to have all modules work together correctly.

[R Shanta]

I "helped" a buddy adjust his speedo on his new 2017 Silverado 1500 for his 35's. Dealership put the lift and tires on, but did not correct the speedo. I thought it was a little strange and chalked it up to incompetence, but then again appearently so am I.

As a result he no longer has cruise control. Specifics

EFILive V2
V8 Version 8.2.5 build 316
V7.5 version V7.5.10 build 323
OS: 12677878
Controller: E92

I purchased a controller authorization code to read out the stock calibration and changed parameter H0105 from 405 to 364 within 7.5. Then performed a full-flash with V8. I saved the stock tune, modified and saved the tire size correction as a different file.

Should have I adjusted H0136 by the same amount?

[joecar]

Post tune file.

[R Shanta]

Joe,

Attached is the stock and adjusted files.

Rob

[joecar]

I'm using V7 build 329, and H0136 does not show up.

[R Shanta]

Joe,

It is in the speedo calculator, parameter for revolution/mile or km. Though everytime it opens there is error: Cannot create file "C:\Program Files (x86)\EFILive\V7.5\Configuration\cal_adjust.txt." Access is denied

I get the same error with all my other tunes, except the speedo table populates, where with the 2017 silverado it does not.

Rob

[joecar]

Ah, I see.

Run the V7 tunetool as Administrator (rightclick->Properties->Compatibility->Privilege Level)

[Blacky]

I "helped" a buddy adjust his speedo on his new 2017 Silverado 1500 for his 35's. Dealership put the lift and tires on, but did not correct the speedo. I thought it was a little strange and chalked it up to incompetence, but then again appearently so am I.

As a result he no longer has cruise control. Specifics

EFILive V2
V8 Version 8.2.5 build 316
V7.5 version V7.5.10 build 323
OS: 12677878
Controller: E92

I purchased a controller authorization code to read out the stock calibration and changed parameter H0105 from 405 to 364 within 7.5. Then performed a full-flash with V8. I saved the stock tune, modified and saved the tire size correction as a different file.

Should have I adjusted H0136 by the same amount?

H0136 is not available in that truck's calibration so you can't "change" it. The speed calculator can't used for that truck because it doesn't support the {H0136} calibration.

Changing {H0105} only changes the speed that is output from the ECM via a dedicate wire or via a message on the CAN bus. It won't change the internal speed that the ECM uses/calculates. It is possible that changing {H0105} will cause a discrepancy between the internal speed used by the ECM and the speed that the ECM is transmitting on the CAN bus. That can cause other modules (ABS etc) to "think" there is something wrong with the way the ECM is measuring the speed of the vehicle. That in turn can cause functions (such as cruise control) to be disabled.

It is probably best to get the dealer to correct the speedo because the adjustment may need to be be made elsewhere (not in the ECM) - such as in the ABS module or in the instrument cluster.

Note, changing just calibrations does not require a full-flash. A calibration flash will update any calibrations that you change. A full flash is only required when you apply an EFILive supplied operating system patch.

Regards
Paul

[R Shanta]

Joe,

Thanks for the tip and cruise now seams to be working.

Paul,

Thanks for taking the time for the explaination. I agree with you that it would be best for a dealer to make the adjustment, however; his particular choice of dealer is not willing to adjusted. Per Joe's and your's suggestion and cal flashing the ecm with just the H0105 seams to be working at this time. My fall back plan is to cal flash H0105 back to stock and assist him with finding a capable dealer to make the change.

Rob