98 F-body speedo change

[1320ft]

Is it possible to change the speedo on a 98 F-body? All I see is one space under "current" with 7.71 lowlighted grey. Then under "new" there is a blank space that you can put a number in but anything you put in comes out invalid. So what's the deal here? I am looking at getting 3.73's in place of my stock 3.23's..... so I am going to need to change my speedometer!

Thanks

[Russ K]

The 1998's use the tire dia/gear ratio. So for your 3.73 gears, take the calculated tire dia 24.903/3.73=6.676, then hit the commit button.

Russ Kemp

[Bill@HPTuners]

http://www.thetuningdoctor.com/HPTun...gearchange.swf

[Russ K]

Bill

1320ft needs to understand that 24.903 is used for the stock tire dia, not 25.7. Using the measured/advertised tire dia when changing the speedo is a common mistake as it raises the WOT shift speeds causing no WOT shifts. Plus the speedo will read higher than the actual speed.

Russ Kemp

[Bill@HPTuners]

The demo is not meant to explain what number go in and more of why they must be calulated a specific way. The same "how do I calculate for new tire size or new gears on my 98 camaro" question pops up about once a week which is why I made the demo just to show people how it works on those pcm's. I can, however, add in a blurb to the effect of "gm uses 24.903 as the effective stock tire height" or something.

[1320ft]

Thanks guys! I knew there had to be a simple procedure So, I am going to need to use the 24.903 for tire diameter? Is that only if I have my stock tire size? When you change tire size from stock then do you use the measured tire size? My car is 98 SS by the way.....

Thanks