The Stovebolt Site Forums Swap Meet Truck Parts For Sale Electric speedo adapter 1960's C-50-80

Here is a NOS GM electric speedo adapter p/n 3828638 I believe it is from the mid 1960's to early 70's in C-50-80 models .$30 + ship

Am I correct in thinking this is the little magic box that makes the speedometer read correctly in both low and high ranges? There's something like this under the dash of my '65 C60, but it's long since been disconnected, so my speedometer reads fast in low range.

Yes, that's what it is...My parts book lists it as;

1963 Series 50 thru 80 w/ 2-spd axle.
1965-66 Series 60 (TILT) (4 cyc. Diesel) w/ 15000, 16000, 17000 2-spd axle.

Mike B