My dealer said that they could not reprogram my DIC to account for larger tires. He said it was not something they could do with any of the Allison equipped trucks. Although I know he's spouting a line of B.S. in that department, is there a reflash for the LLY trucks yet? I have 285 tires fitted and my truck came with 245's. I understand that there may not be a reflash available for the 285 size, but I figured if I got it set to the 265 setting, it would be better than nothing. Anyone know more than my dealerhttp://www.dieselplace.com/forum/smileys/Clown.gif


GarEdited by: biggar

You can reprogram your truck with a programmer to have the speedo read right for the tires you have added. Just my 2 cents.

Thanks. I'm waiting for the Edge Juice setup. Hopefully that will allow me to set everything up the way I want along with a nice powah boooost.





Gar

Biggar,


I also put on 285's, third day I had it. I'm a tech so I went in back to the shop where I bought my truck from and asked about re programing my tranny to 265's since the one SRW has that size. He told me GM won't let the tech 2 scan tool re flash with the allison. He thought it was bs too. So your not alone. He also told me that they can't do warranty work for driveline or motor issues unless 245's are on truck. I told him I sold them and if the issue arises I'll have to talk to the SM. I told the salesman what I was doing and of course you always get the oh that's fine routine. Guess we'll have to wait for programmers. Also with the juice can you re program for tires?

It is BS. We progrmammed my truck for 265's with the Tech II at the dealership. Speedo is dead on. Since the mechanic is a good friend of mine, I will not have to worry about tire size and warranty, but will just bolt on my 245 Winter Blizzak tires/wheels if ever needed...

It is BS. We progrmammed my truck for 265's with the Tech II at the dealership. Speedo is dead on. Since the mechanic is a good friend of mine, I will not have to worry about tire size and warranty, but will just bolt on my 245 Winter Blizzak tires/wheels if ever needed...


It's not BS. It has been confirmed that it can't be done by, many, many, many GM mechanics. Your truck MIGHT be different because a 265/75/16 is available from factory on 04 in a 3500. But on 03 and older for sure you can not correct the speedo to 265's with a tech II.

Max Power.


Biggar was asking about an LLY, which I also assumed since this is the LLY section of the forum... I do not know about the 03's since mine is an LLY as well.

Max Power.


Biggar was asking about an LLY, which I also assumed since this is the LLY section of the forum... I do not know about the 03's since mine is an LLY as well.





I am pretty certain that they can't reflash even on the LLY. Hopefully Eric will see this and confirm one way or the other.


Likely what happened with yours was they reflashed for the ABS and the speedo is only off a a mile or two. Either that or it was off a few miles before you started and the tires were enough to correct it.

How did you confirm that your speedo is accurate?Edited by: Max Power

Sammy,


We just went through this question and the thread is just below this one:


http://dieselplace.com/forum/forum_posts.asp?TID=9761&PN=1


Included there is a copy of a post by Freddyo of a GM dealer bulletin saying no other calibrations for different tire/wheel combinations are available:


Following is the text of a Bulletin sent to dealers a few days back.

-----------

Info - Inspection of Tire and Wheel Size Prior to Diagnosis of Transmission Shifts, Poor Performance, Speedometer, Cruise Control Concerns #01-03-10-010C - (04/20/2004)

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

2001-2004 Chevrolet Silverado Pickup Models

2001-2004 GMC Sierra Pickup Models

with Allison® Automatic Transmission

This bulletin is being revised to add the 2004 model year and additional vehicle/tire sizes. Please discard Corporate Bulletin Number 01-03-10-010B (Section 03 - Suspension).

Proper diagnosis of engine, transmission, speedometer and cruise control concerns must begin with an inspection of tire/wheel size.
• The 2500 series trucks have LT245/75R16E tires as standard equipment.
• The 3500 series trucks with dual rear wheels have LT215/85R16D tires as standard equipment.
• The 3500 series trucks with single rear wheels have LT265/75R16E 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

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.


__________________
freddyo

The only question that I would have is why did the Tech II allow me to flash my truck with the 265 (I was watching over the mechanics shoulder as he did it), and why is my speedo right on?


Not arguing the validity of the bulletin, just confused as why it appeared to calibrate just fine on my truck. Oh well, I suppose I should not complain as long as it works just fine.

The only question that I would have is why did the Tech II allow me to flash my truck with the 265 (I was watching over the mechanics shoulder as he did it), and why is my speedo right on?


Not arguing the validity of the bulletin, just confused as why it appeared to calibrate just fine on my truck. Oh well, I suppose I should not complain as long as it works just fine.




It is my understanding that the adjustment you saw would be related to abs and not the speedo correction.


The reason you are seeing your speedo right on is because the difference between 245 and 265 tires is only 1 or 2 mph. I am not sure what you checked it with but it could have been off to start with and the tires corrected it or perhaps the margin of error is high enough that you can't see that you are out a mile or two.

Im gonna try and check mine with a GPS !

I found this on the Allison web site:

Q. Speedometer / Tires - Can my speedo be re-calibrated after I install larger tires?
A. Speedometer calibrations are only available for tire sizes offered as original equipment. Please consult your GM dealer about correcting speedometer output when tire size is changed.

NOTE: Changing the calibration to correct speedometer readout does not change the TCM calibration, and thus it does not compensate for the adverse impact on transmission operation.

Q. Speedometer / Tires - What effects will big tires have on transmission operation?
A. The TCM calibration is based on factory tire size and rear axle ratio. Changing either of these parameters will have some adverse impact on transmission operation, including features like grade braking and shift stabilization. For instance, we have noted that when P285 tires are installed that the transmission generally does not shift to 5th range when towing heavy loads.

Also, when it comes to extra power upgrades, Allsion is not taking any responsibilities:

Q. Increasing Engine Power - What about transmission warranty?
A. Warranty on the Allison 1000 Series™ in GM pickups is administered by the Chevrolet or GMC divisions of GM, not directly by the Allison division of GM. Please consult your GM dealer regarding questions about warranty coverage.