factories with all gauges “matching,” i.e., either all AC or all Stewart-
Warner. This may not have been the case, however, and some
instrument panels may have been mixed, depending upon the supply of
components. In any event, many M-series instrument panels ended up
getting mixed in service as the gauges wore out and were replaced.
While one might prefer an all “matched” panel for appearance sake, it is
still perfectly proper to combine both types of gauges in your restored
military vehicle.
Figure 4
For World War II-vintage military vehicles using the “standard”
instrument cluster (Figure 1), the difference in needle shapes and face
markings is sometimes more pronounced, (check the difference in needle
styles between Figure 1 and Figure 2, for example). Also, some World
War II speedometers had resettable trip odometers, so a bit of research
will be required for accurate restoration.
While this article refers to speedometers, the same techniques may be
applied to the service and repair of mechanical tachometers.
Virtually all speedometers are calibrated the same. What this means is
the gear ratio that determines how “fast” they read is down in the
transmission or transfer case (Figure 4) and is transmitted up to the