Re-flash Allison Or Upsizing Tires

[GeeJay]

I had my dealer upsize the tires on my '07 2500HD from OE 245/77R16 to 265/75R16 which is OE size for the '07 3500HD.

 

I had asked them to re-flash the Allison for the size change but when I picked it up the said they had nothing but problems with re-flashing the Allison so won't do it anymore.

 

Seems to me that should be a no-brainer!

 

What say the experts?

 

GJ

[minibike132]

I had my dealer upsize the tires on my '07 2500HD from OE 245/77R16 to 265/75R16 which is OE size for the '07 3500HD.

 

I had asked them to re-flash the Allison for the size change but when I picked it up the said they had nothing but problems with re-flashing the Allison so won't do it anymore.

 

Seems to me that should be a no-brainer!

 

What say the experts?

 

GJ

 

It's not a no brainer and definately not something that is going to happen for free. The dealer does not have access to the flash data to change tire size, it has to be purchased. The dealer calls techline with a vin and the relevent tire swap data. They upload the flash data to the dealer and charge the dealer account for the flash. That flash gets passed on to the customer + the time that it takes. Your looking at a half hour on the phone + up to an hour to program all relevent modules...if there is no problems encountered during programming.

 

I can't say that I ever had any difficulties flashing any Allisons but I never flashed one for a tire change. If memory serves (I have not done any tire change flashes in a year or more) the trans is not what takes the flash. It should be the PCM/ABS and Cluster modules.

 

I'm sure someone will chime in with programmers that will get the job done for you at a much cheaper price then it would cost to do it right.

[gmtech4]

+1 ,not the tranny

[GeeJay]

I'm sure someone will chime in with programmers that will get the job done for you at a much cheaper price then it would cost to do it right.

 

I have been researching a number of programmers but all indicate they have no programming for the Allison, e.g. tire size, shift points etc, as it has a separate computer.

 

I emailed a couple for clarification and they both confirmed this in response.

 

Since my post I have had an email reply to my inquiry to GM.ca Tech Support ,who advised they will phone me next Monday. Hopefully they will give me a straight answer and not avoid the issue by citing corporate policy etc.

 

GJ

[Nytemare]

In the end dude...your out by 3.9% on your speedo. That means at 100km/h you are actually going 104. I never re-flashed mine when I changed the tire size...I'll do it when I get HP tuners plugged into it, maybe this summer.