Speedo is off , How do I fix it ?
i've got this same problem as well....as has been stated before i assume this is a very common thing. mine is off by about 5 mph at lower speeds and 10-12 mph off at higher speeds (i.e. 60-70 mph) the Tach is also off. I found out it was off when i had it hooked up to HP Tuners doing some logging. so the PCM is putting out the correct mph/rpm....but my gauges aren't. How could this problem be fixed? and how would you go about recalibrating the PCM if that is the fix?
I was told on another forum and some one said I could have aftermarket gears that could be throwing off my speedo . My RPO said GU6 so 3.42 but in 6th gear at 2,000 rpm my car is doing 90mph . So does my car have bigger or smaller gears ? Plus how can a tuner figure out the gears I have because some one suggested a tuner can adjust my speedo.
I was told on another forum and some one said I could have aftermarket gears that could be throwing off my speedo . My RPO said GU6 so 3.42 but in 6th gear at 2,000 rpm my car is doing 90mph . So does my car have bigger or smaller gears ? Plus how can a tuner figure out the gears I have because some one suggested a tuner can adjust my speedo.
http://www.kabamus.com/garage/gears.html
The tuner will be able to adjust the parameters to match your tire size & gearing. However I did the same thing and the speedo was still 5MPH fast at 60MPH. I think I adjusted the pulses per mile to get it closer.
So with that I am guessing I have 3.42 gears in my rear end but the car is programmed to 3.73 's ?
What do yall think ?
Edit : I want to know because my car may have less miles that what the odometer reads .
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Verdad Gallardo Not sure if you can see the pinion gear this way, but it may be an alternative. Buy some replacement gear lube and the additive if required. Pull the diff cover, count the ring teeth, and count the pinion teeth, then divide ring by pinion to get your ratio. Re-seal cover and replace fluid.
Speedo FIXED 
I took my car to a tuner and the tuner said my car hasn't been messed with . and the aftermarket wheels would not cause that big of a skew in the speedo . But long story short is was fixed by messing with the tire size.
I took my car to a tuner and the tuner said my car hasn't been messed with . and the aftermarket wheels would not cause that big of a skew in the speedo . But long story short is was fixed by messing with the tire size. 