Speedo/Odometer Recalibration

[birdogn]

I'm new to the group, and will finally pick up my new 03 on Thursday....Pewter GMC Ext Cab D/A SLT with everything except extended mirrors, 6 changer CD, and Full feature seats. (Was too late for an 02 and too early for the CD changer and the extended mirrors. Apparently there is still a problem with the wiring harness to add the Power Vision Towing mirrors on an aftermarket basis. (this according to my dealer and the Power Vision website)

First additions will be fifth wheel hitch, a spray-in liner, and a replacement tank. Thanks to the class action on 97 tanks advertised as 32 gal, but only being 26.9, I have $750 towrds the new truck. Will run up to to Transfer Flow in Chico, and have the stock tank replaced with a midships 45 gal tank. Then as funds allow, Wheels, Duramaximizer, exhaust temp gauge. Is anyone familiar with recalibration when going to larger wheels/tires?

[RyanbabZ71]

How much bigger are you going?  There are a few aftermarket programmers (which do other things along with tire sizes).  The dealership cant go very large.  They couldnt recalibrate my 285s so i bought a hypertech programmer for $279.  I dont know if they make one yet for the D/A

 

Congrats on the new truck.  

[TxDoc]

Apparently, the HD  with the D/A combo will not be recalibrated by dealers (may depend upon who you know and who you are). There is a TSB regarding this. Here is some info on other's responses:

 

"

Yesterday I had my truck (2001 2500HD 8.1/Allison) in to try and get an updated calibration for the Allison which they did take care of. Today the service manager calls me and said they just received a bulletin from GM that states that any truck with the Allsion transmission that has tires larger than stock (mine has 265-75-16) will have the warranty voided for the transmission.  I informed him that my truck was purchased directly from them with these tires on them. They send trucks off to a custom shop to have certain upgrades done. They said they are informaing all customers that bought trucks with the upgraded tires to bring them back and have the original size tires put back on at the dealers cost. I told them that this was no deal because I bought this truck with these tires because I tow a trailer off road on a regualar basis and need the more aggressive tire. I would have never bought the truck if I could not upgrade them. At that point he said that he would consult with some other management there at the dealer and get back with me. WOW! I really don't know what to think at this point."

 

The TSB:

 

Info - Inspection of Tire and Wheel Size Prior to Diagnosis of

Transmission Shifts, Poor Performance, Speedometer, Cruise

Control Concerns #01-03-10-010

Inspection of Tire and Wheel Size Prior to Diagnosis of Transmission Shifts, Poor Performance, Speedometer, Cruise Control Concerns

2001-2002 Chevrolet and GMC C/K Pickup Models (Silverado, Sierra)

with Duramax™ Diesel Engine and Allison® Transmission

Proper diagnosis of engine, transmission, speedometer, and cruise control concerns must begin with an inspection of tire/wheel size.

The 2500 series trucks have LT245/85R16E tires as standard equipment.

The 3500 series trucks have LT215/85R16D tires as standard equipment.

A truck that has different tires and wheels will have Engine power/performance concerns, Transmission shift concerns, Speedometer registered speed concerns, and Cruise Control concerns.

Before any diagnosis is performed for these types of concerns, inspect the tires/wheels for the proper tire and wheel combinations.

If a truck is found to have other than the above listed tire sizes, no further diagnosis should be undertaken until the original size tires and wheels are reinstalled

on the truck.

The Engine Control Unit (ECM) and Transmission Control Module (TCM) use (RPM) and (VSS) inputs as operational parameters for engine torque,

transmission shifting, cruise control operation and speedometer indicated vehicle speed.

Calibrations for different tire/wheel combinations are not available.

Therefore changing of tire and/or wheel size should not be undertaken by dealerships or truck owners.

Warranty Information

Reinstalling the proper wheels and tires on the vehicle, prior to performing any type of diagnosis of the truck, would be considered truck owner responsibility

and not a warranty repair.

 

Hope that helps, but it may not be what you really want to hear.  Check out the dealer and see what they say.

[Shaners]

Welcome to the forum and congrats on the new rig.

 

Both replies are right on.  The dealer can but won't reprogram your speedo/odo calibration.  A HypertechIII  will take care of it for you depending on how big of tires you choose.

 

I'm surprised that the dealer said you couldn't get the power towing mirrors.  My local dealer has had a crewcab on his lot for at least a week with the power towing mirrors.  I sure wish I had them over my manual towing mirrors.  They look like they are sweet.  I think the sticker price on the new style mirrors was around $250.

[Kelly]

Why would different size tires void the transmission warranty?

 

This would be in violation of a Federal Warranty Law from what I've read on other websites.

 

Sorry, I can't remember the proper name.

 

Can another member post additional information about the Law?

[TxDoc]

It is against the law for a manufacturer to require the use of a specific BRAND of air filter, tire, etc., unless it provides a replacement air filter, free of charge, under the terms of the warranty. For a more thorough discussion of this law known as the Magnuson-Moss Warranty.  But, this apparently will affect their efforts to diagnose a problem. Re-read the TSB and it will explain their reasons:

 

A truck that has different tires and wheels will have Engine power/performance concerns, Transmission shift concerns, Speedometer registered speed concerns, and Cruise Control concerns.

Before any diagnosis is performed for these types of concerns, inspect the tires/wheels for the proper tire and wheel combinations.

If a truck is found to have other than the above listed tire sizes, no further diagnosis should be undertaken until the original size tires and wheels are reinstalled

on the truck.

The Engine Control Unit (ECM) and Transmission Control Module (TCM) use (RPM) and (VSS) inputs as operational parameters for engine torque,

transmission shifting, cruise control operation and speedometer indicated vehicle speed.

Calibrations for different tire/wheel combinations are not available.

Therefore changing of tire and/or wheel size should not be undertaken by dealerships or truck owners.

 

 

The towing mirror problem is due to Production Holds:

 

Sierra 2500 8 - 10 Availability is limited for Engine, 6.6L V8 diesel (LB7).

Availability is limited for Mirror, extendable exter (DF2).

 

Sierra 3500 8 - 10 Availability is limited for Mirror, extendable exter (DF2).

[TxDoc]

Ran across this post--Click Here

 

It may be an option for you:

 

"I've been carrying the Superlift TrueSpeed speedometer recalibration unit around in the truck for the last month and finally got around to installing it. It was a fairly simple install with the exception of the c2 connector on my 2002 California truck is clear instead of red. Any way we got it installed and after 3 or 4 stops to make fine adjustments the sppedometer / odometer are whithin .3 mph at 75 mph according to my GPS.

I calibrated it according to the published tire sizes from Fireston/Bridgestone. Stock Steeltex 245/16 at 30.5 diameter and Bridgeston Dueler 285/15 at 32.9. These were obviously off either by stock being smaller or new tire bigger because I had to dial in more adjustment.

 

I had always figured my fuel mileage at about an 8% difference. But last tank I used after the install showed it to be about a 10% difference. last tank was about 125 city 300 highway came in at 17.9 mpg.

 

For all you guys out there that want to recalibrate the speedometer this thing works! It also has a switch so you can run a second size of tire wheel and have your speedometer be on with the flic of a switch. "

[birdogn]

Re: mirrors....Initially they weren't available on new because the factory wasn't ramped up (My rig was manf. in early July). Until the wiring harness is resolved, they're not available as aftermarket. Sticker price direct from Power Vision is $459. .....without install !!! :angry: