speedometer gearing

[bk65]

I rebuilt my speedometer unit with parts from another truck. It works fine except it's off about 20%. My truck has the factory 4speed and factory 3.73 axles. If my math is right, the speedo would read dead on if I had 4.56 axles on it (which is what the donor truck had). So my question is, is the gearing different in the speedo unit, or do I need to swap the speedo cable drive gear on the tranny?

Thanks

P.S. Still searching for a picture of a "factory" transfer case shift lever boot for a 60-66.

 

[GreatNorthWoods]

BK,

You need to swap the speedometer gear. If you know how many miles per hour it's off, you can approximate which gear you need. If it reads too high you need a gear with more teeth and if it's too low you need a gear with less teeth. One tooth is worth about 5 mph, so count the teeth on your present gear and make adjustments from there.

 

[bk65]

Drive gear in the speedo or at the tranny?

Thanks

 

[GreatNorthWoods]

The speedometer gear in the transmission...

 

[bk65]

Thanks!