I just talked to a dealer in IA that used the scan tool to recalibrate the computer for larger tires. They did this because a customer complained about fuel mileage and he went from stock tires to 265's so the dealer said they changed the tire size and then drove 20 miles and the DIC went from 13 average to 17-18 average. I know 20 miles is not much but the customer was happy so far. I will update when he has more miles...


I asked the Service Manager why other dealers say they can't recalibrate and he could? He didn't know why but said some things like ABS reasons you can and that must have also corrected the DIC.


Has anyone else done this???

The difference between 265 and 245 (stock) tires is less than 4 % so I do not understand why there should be such a difference on the DIC and real fuel milage - if any. Must be some mistake somewhere in the customers fuel milage calculation. http://www.dieselplace.com/forum/smileys/Confused.gif Edited by: mahalkita

mahalkita, you are right. I am in the process of seeing if my dealer will do this to my truck since I have the same tires (265) and then I will have a better answer...

NOPE, I tried my dealer. They tried everything in their computer. There are a ton of sizes to use to recalibrate for bigger tires, but with the allison tranny you cant recalibrate. THere is even a service bulletin stating that it cant be done now. They printed it out and I saw a copy of it somewhere in here that someone posted. I guess you have to buy a programmer. Like the Bully DOg PuP or the Predator. Any ideas which would be the better of the two. The predator is supposed to be released soon. What would you buy. I already have the edge/*** but that wont recalibrate my speedo and odomoter or my mileage.

Ahhhh. another case of misleading information from the dealer....


My tech 2 is updated to the most current and nope, still cant do my own 03.....


Gotta love the dealers that dont know..... and those that buy it..http://www.dieselplace.com/forum/smileys/Cry.gif

Thanks dmax!http://www.dieselplace.com/forum/smileys/Clap.gif

I just took my truck to a dealer and "had them" reprogram the computer for larger tires. I thought they were able to do 265s but no larger. I have 285s and inquired about that but they said they could only do 265s (just as I suspected). So did it really do nothing?


I know the info here is a heck of a lot more accurate than any dealer i've visitedhttp://www.dieselplace.com/forum/smileys/Big Smile.gif


Hmm, if the 3500 SRW trucks with d/a's come with 265s, couldn't you use the same code for a 2500hd?

As I recall, dealer can only reprogram tire size for ABS input.

OK maybe it wasn't the Allison that gets recalibrated but like I said it had something to do with the ABS and supposedly what ever number they changed affected the DIC read out.


dmaxallitech, is there a setting that can be changed for tire size that would reflect in the DIC read out like this guy is claiming?

Ok so how do the programmer work that reprogram the speedo? Do they really do nothing as well? Just curious, getting ready to run 285's and I am curious about this. If the TECH 2 and dealership can not do it then how can the programmer?http://www.dieselplace.com/forum/smileys/Confused.gif

the tech 2 can do it, buts its not allowed to. The aftermarket stuff can do it becuase it is allowed to.


ABS calibrations can be changed, but that is not a good thing when your abs calibrations and your vss calibrations dont match, it COULD lead to some funny abs stops.

I run 285 BFG ATs and haven't recalibrated - I get very funny ABS stops - had to do 2 in the last 2 weeks - one I was tired and didn't see red light 'til almost too late, the other to avoid a kid on a bike. Both stops the same - ABS kicked in, then out, leading to a series of intermittent lockups/chirps, not a true abs stop...

Ok I was just making sure I was not missing something. Thanks

In order for GM to provide calibrations like this, they'd need a reason. Like offering these size tires on the vehicle in the first place. THEN they would need to get it emissions certified for EACH size calibration. Lotta dicking around in their eyes I'm sure...

We you would think they would offer larger tire sizes to begin with. Most people are going to end up that way in the long run, so they could try and help out some....http://www.dieselplace.com/forum/smileys/Confused.gif

JK,


I agree. Plus they would probably have to change/limit towing capacity, power management and a host of other things as well. Just too much work. They probably figure there are a lot of vehicles that will remain stock, the ones that aren't stock, they won't have to worry about because we all will figure out what to do anyway, so they won't have to. They win all the way around.


GMC2500HD,


It sure would be great if they offered them that way. . . I guess we can hope for the future.


Dennis

So is the speedometer and ABS not working right on these conversion trucks like "Regency" that can be purchased new off a dealer's lot that come with 285's?