The previous owner of my 91 dak 4x4 put larger tires on,which was a great deal for me.But I found a problem.

The truck actually runs 10kph faster than the speedometer reads.This also throws off the odometer and trip meter.

Am I stuck with this flaw,or is there a was to re-calibrate the speedo for the bigger tires?

 

Well I know 92 daks and up Jet and Accel make speedo calibration units for bigger tires and different gear ratios. But haven't seen one for 91 id take it to a tranny shop and ask them if they know anything.

 

Most large cities will have a speedo shop that can do it for you.

Or do it your self.
1. Get a GPS, handheld work too. Figure out EXACTLY how much it is off at 10MPH increments. Write it down.

2. Then figure the percentage in between the old and new speeds at each 10MPH increments.

3. Get the average of the percentages.

4. Then take out your speed sensor and remove the Speedometer Pinion. Find out how many teeth you have on it.

5. Then add in that percentage to it, to get your new gear tooth count.

6. Then get a new gear with that many more teeth. You can get the new gears from a Dodge dealer. Some can be $10 some can be $80.

Note: 93 down the speed sensor will have a cable attached with wires. 94-up will just have wires.
The 2nd pic below is 4wd. 2wd will be in the rear of the transmission in a similar location.

 

Thanks guys.Good to know it can be easily remedied.I'll hunt around here for a shop though.My math skills are not good enough any more to figure out percentages.

 

I have a cable driven speedometer as well. My brother said he was able to turn a crank on the speedometer when he had the dash open. It used to be 10 miles fast, now it's only 6 mph fast.

 

Didn't think to look there.I'll have a peek for it when I pull the cluster to do some wiring.