Two tickets and a drop in mileage, I think my speedo is off by about 7 mph. How do I fix this? Never calibrated a speedo before.

 

Superchip programmer can fix that

 

cheaper fix

 

well there is the truespeed calibrator

Rickson Truck Wheels and Accessories

 

There's at least a half dozen different brand of boxes out there that do this. The dealer can also do a flash for you that will recalibrate this.

Now I gotta ask the real question here. I see your runnin an Auto tranny, RUH ROH. How big a tires are you runnin. You know that if your speedo is off then so are your shift points on your tranny. No problem for us manual tranny guys but could be disasterous for an auto if those are off to far.

 

Just put on new Dakota P265/75R16. I didn't change tire size. Tranny works, truck rolls forward and backwards.

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Reflashing the computer resets for a new tire size?

 

The dealer can do a re-flash to adjust the computer to the tire size you want. If they are smart enough to figure it out that is.

 

Something does not add up. At what speed is it 7mph off??

What is the gear ratio and what was the tire the new one replaced?

For instance, if your speedo was correct with 245-75/16 and you went to 265-75/16 that is an increase in unloaded diameter of 3.75%. Or, at 60 MPH indicated, you would be going 62.25 MPH.

That does not account for loaded radius, ect.

If you are 7MPH, something is clearly wrong. We need more info.

Dave

 

yeah the only way to throw your speedo off is to change tire diameter or to change the gear ratio in the pumpkins

 

Well you could use a GPS or a Scangauge II...