Calibrating The Speedometer
#1
Diesel Enthusiast
Thread Starter
#5
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.
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.
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torquey (02-23-2008)
#6
Diesel Enthusiast
Thread Starter
#7
#8
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
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