From a different thread-
Originally Posted by Joe H
The odometer is gear driven right off the cable end. It will always be a direct reading off the transmission gears. The speedometer needle is magnetically driven off the cable end. If the magnets get weak or there is damage to the hair spring, the needle might not show an accurate reading.
Joe
1955 2nd 3100; 3 spd; 215/70/15 tires; 12V--- The truck's speedometer reading is not accurate and I would like to know options to get it to show an "accurate" reading.

The odometer functions and is correct. This is verified by known distance driving and also by a lead vehicle (pace car) readout/comparison.

The speedometer reads 12 MPH at a known speed of 30 MPH, and the speedometer reads 28-30 MPH at a known speed of 45 MPH. The speedometer does not move at all until I get to 2nd gear speed (or if I am driving too fast to be in first gear; I checked). The speedometer needle doesn't flop around or act erratic. I replaced the speedometer driven gear (inserted in transmission) with the exact tooth count plastic reproduction, however, I do not know if the original ever functioned. The speedo cable was severed when I got the truck.

Thanks for any guidance; worst case scenario, as of now, is I'll just know 30 MPH readout equals 45 MPH. Of course I do prefer the thing to be accurate.

Brad

Edit (Chief has made me look for details, lol)- a new speedometer cable is attached now, new and/or rebuilt gauges in the cluster, and as mentioned, I connected the speedo cable.

Wrench Fetcher, PhD