Questions about adjusting Speedo
 

Okay I have had this 2000 GT for about 5 months now... The speedo is a constant 9 MPH fast... Doesn't matter if I am going 25 or 125. I am assuming that the car has had gears installed at some time before I bought it although I am not sure how to tell what gears have been installed or even if any at all. I bought a used Diablo Predator from a guy at a STEAL for can anyone tell me how to adjust the speedo with it? I have read in quite a few forums that this can be done, but I have also read that you have to change the speedo gear... Any help would be appreciated.

if you use the gear calc on the gear thread sticky found at the top of the general tech section you can plug in your tire size,speed, and then change the gear ratio till it matches what your car does and you will know for sure what gears you have. Or you can count have many times teh wheels turn per one revolution of the driveshaft. i would just go do 40mph in 4th gear and see the rpm and then use the calc to see what gears it has.

99 and up dont have speedo gears, you have to get it tuned or get a speedcal or something similiar

Can it be done with a Diablo Pretator or do I need to get a speedcalc?

you can change it with that tuner.

just to interject... my experience tells me that gears change the offset of the speedo in varying degrees depending on how fast you're already going (as a %age of your actual speed).

I'm betting someone actually pulled off the speedo needle and put it back on wrong. It's a bitch to line up just right.

Mine is now off by 5mph (over-reports) deliberately. Now I can always go 10 over and not have to worry about tickets. It helps keep me from actually speeding much.