How does the odometer track with mileage markers on the highway?
The odometer is gear driven and is a direct reading from the transmission, the speedometer is magnetic driven and relies on magnetic pull to spin the needle. A odometer error is due to transmission gearing, both odometer and speedometer error (if off same amount)is the gears, and just a speedometer error is in the speedometer head.
Drive the truck ten miles on the interstate, watch the odometer closely, then figure the difference between the two after ten miles. Say you lost 1 mile out of ten, thats a 10 percent error. Now count the teeth on the driven gear in the trransmission and reduce the number by 10 percent.
Smaller gears turn faster which add miles, larger gears turn slower and count fewer miles.
If the odometer is close and speedometer is still off, your speedometer head need cleaned and/or repaired. Most will loose a percent the faster you go, but around 35 they should track right on. As the magnet gets old it weakens and just can pull the needle like it used to and if the needle assembly is dirty, it just adds to the problem.
Joe
