Originally Posted by poodles
I just put new tires on our mh, I went one size up and now I have about a 10% difference in speed and milage on the speedo. Speedo says 55, gps says 60. Also the mile markers are about 1/10th of a mile out.
Can I reprogram the speedo or do I have to have a tech change something on the sending unit?
Thanks in advance.
This is a common thing with the 4X4 crowd...
For modern rigs, the mod is in the ECU (not the sending unit). You can "flash" the ECU for tire size and some other things depending on the programmer you buy...or save the $$ to buy a programmer and have a shop do it for you.
On older rigs, the sending unit was replaced to modify the signal or, for really older rigs the tranny gear is changed to change the speed of the speedo cable.