Reprograming the Allison and Oversize tires

[TH]

I was told that you could recalibrate the speedometer for 285/75R16 tires in the 2500HD Duramax with Allison by using the factory program settings for the 245/70R19.5 tires that are in the T6500 Diesel truck. Tire diameter is the same and the dealership should have these tires in their computer. This would be a great fix if it works! :D

Question is, does anyone know if its possible to reprogram to 19.5 tires that come stock in a T6500 GM truck?

If so, would these changes then affect the Allision and make it think its in a T6500 truck and screw up my shift patterns because it thinks its linked to the T6500 engine? The T6500 truck comes with a Duramax with only 240 hp but something like 840 ftlbs of torque. I'd hate to have that setting for my Duramax.

Will changing the tire settings to the 19.5 size also create changes in the power output from my engine?

Anyone out there know for certain what happens? :confused:

[atvpilot]

I had my speedo recalibrated by the dealership my buddy works at. The only problem was the computer didn't have a setting for the 285/75/16 only for the 265/75/16. So I went with that. Sorry to starpped to drop 400-500 bucks on a reprogrammer. jut tryin to be honest :D

[TH]

Thanks for your reply...what does your buddy say about using the factory settings for the 245/70R19.5 tires? They are the same diameter as the 285s.

[Craig M]

Talked with a guy that had the 19.5 tires on his Duramax dually. Asked him if he had his speedometer recalibrated. He said the dealer would not let him change. He says he is about 10% off. One advantage is he now gets a warranty for 110,00 miles instead of 100,000. By the way the dually really looked nice with the 19.5 tires. He had the 10 hole aluminum Alcoa classis wheels, and that combination was trick! He had Michelin tires. He pulls a 35' 5th wheel trailer with it and has no problems.