I know there are alot of tire size threads on here, but one thing that hasn't been covered is the difference between the('05) 2500HD and the 3500 SRW....
The 2500HD has LT245/75R-16's and the 3500 SRW has LT265/75R-16's.
GM says no calibration change is available for tire size changes, but what is the difference between these trucks??? Rear end gear??? Tranny ratios???? Is it all in the programming? If this can be determined, it may create a fully functional solution, with no speedo accuracy problems for someone like myself who just wants a little more meat under the fenders.
Anyone know?
Ed

Are you really an ASE and GM Master Technician? Just curious because I was thinking you would be able to answer that. It is all in the programming on the truck when they make it. They decide what tires to install then program the truck to read those tires. They say they can not reprogram the truck however I know a few people that have had something like that done. I will see what else I can find out...

Are you really the Diesel Place Houston Chapter President, because you don't portray the image that I have come to expect from members here?

Personally, if all your swapping to is 265's, then I don't feel any calibration is needed. Results have shown the speedo is more accurate with 265's on anyway. There's not that much difference in diameters between the two.

We'd need to hear from some GM techs as to the ability to "tune" a 2500HD to 3500 SRW specs when it comes to tire size.

Interesting.......you mean fool the programming into thinking it's a 3500 rather than a 2500?....that's way beyond me. Might be some ABS and other side issues....don't know.
But I can contribute this thanks to one of the guys that posted a tire conversion excel page.

245/75/16......30.469" Dia........9.646" Width
265/75/16......31.650"............10.433"
285/75/16......32.831"............11.220"
305/70/16......32.811"............12.008"

This is formula results....don't know how close it is in real life....fairly close I would assume.

IIRC they can reprogram for 265's thats why its ok and dic is correct on the 3500's - other than that, its just a bigger payload, same power, same tranny... On a side note, i would think that if you were an ASE / whatever, then you would probably have some type of info on this since its accesible especially in your field - no need to take it the wrong way, i think that most people might question it

The dealer reprogramed my speedo to 265s using the Tech2.

We'd need to hear from some GM techs as to the ability to "tune" a 2500HD to 3500 SRW specs when it comes to tire size.
I just realized that AutoEd is a "GM Master Technician".... :rolleyes:

As said above, cant you find this info out yourself at work? :confused:

All the other GM Techs on these forums are VERY knowledgeable about these things.

Amazingly enough, very little service information pertains to factory options, such as tire size, gear ratios, etc. Even good parts men want to know what ratio you have or what ring gear size you have before looking-up parts. The info is just not there in most cases. That is why I have inquired of you all for the "hot-rodder" type of info which comes from actually experimenting with these trucks.
If you want to know how to repair a genuine problem with your factory configured truck, I can find out more crap than the average person could comprehend, however.
Ed