99 suburban square body speedometer change

[camaroguy28]

I have a 99 suburban 5.7 vortec square body. I changed tire sizes on it, from stock size which is 235/70r16 to a bit taller tire 265/75r16. The issue I am having is that I cant figure out where the tuner got its number from for the tire size. When I open the tire wizard, the gear size is 3.73 which is still the gears I am running, but the tire size in that section is 0.74. I have tried dividing tire size by gear and all sorts of other combos and cant get anywhere close to the number that is in the stock section. if someone could please take a look at this I would really appreciate it. This is my wifes daily and I would prefer for the speedometer to be more accurate. From what we can tell, the speedometer is off by about 5mph at 70. Thanks for any help in advance. I tried to post my current tune file, hopefully that helps.



1999 suburban-cat.hpt

[Fast4.7]

I gave up trying to fix my brothers 99 Tahoe with HP Tuners and used Tunercats OD2 to fix it. Something is wrong with the HP Tuners stuff for the Black Box. I would contact Bill@HpTuners on here and see if he can help.

[camaroguy28]

ok, thanks for the input. I knew it looked strange, but figured I was just not smart enough to figure it out lol.
Edit: just tried to private message Bill, and it gave a message like he has chosen to not receive messages, or cant right now. hopefully he will come by chance, or someone else will chime in.

[Russ K]

Change the VSS P./Rev-Trans from 1.0000 to 40.0000. Then adjust your tire size in the Gear/Tire Wizard.

Russ Kemp

[camaroguy28]

I just made those changes and everything looked much better in the gear/tire wizard. Thank you very much, just have to wait until my wife gets home with the burban to see if it puts the speedometer dead on. Just out of my own curiosity, how did you know to change that value from 1 to 40? Again, thanks for all the input and hopefully this helps someone with the same problem.