I have a SCT X4 and am trying to figure out how to make my speedometer correct with my 37" tires...I got the SCT to fix my speedo and for the fun factor but mainly to fix the speedo and shift points...I also got custom tunes from gearhead while I was at it. (love the SRL+ by the way!!!!) Gearhead said they have heard this from a few other customers using the X4 so they called SCT themselves and they said SCT engineers were aware of the problem and trying to fix it, but when I call the tech support they they are clueless and unaware of this...tech support also sent me a "stock custom tune" that is doing the same thing...

While loading up the tune and putting in my axle ratio of 3:73 and tire revs of 560 (562 per Toyo's specs) my speedo is off still... truck shows 55mph GPS shows 63mph...

anyone have any insight or give me direction to fix my speedo? if it was only a few mph off I wouldn't care much, but 8mph off at 55 and it just gets farther off the faster I go...

I have found a Hypertech in-line speedometer calibrator that plugs in to the back of the speedo behind the dash which I think will work but i'm not throwing any more cash ($229) at this till I get some solid info...also don't know if this will screw with my tuning that I have already...

Thanks Guys!!

 

So the X4 changes speedometer now? Thats pretty neat...i have an X3 and i had to use AE to change my speedometer. On the X3 all you change is the tire revs which affects shifting or something

 

I was able to change tire size and correct my speedo on my X3. I did it when I changed my tune to a Innovative Tow tune for a long trip I took, and it kept my corrected tire size when I switched back to extreme street.

 

Not sure about SCT, but some tuners will only recalibrate the speedo up to a certain size tire, for example, while looking for a tuner for my new truck, the Flashpaq (superchips) stated tire calibration from 29" up to 34", not sure of particulars on this. Some of the tuners simply stated that it had the capability recalibrate the speedo, no diameter limits mentioned. I plan on running 35" on the stock wheels, which tuner could I use to recalibrate my speedo?