Name this chevy speedo cable part
 

Can anyone tell me what this device is and why it is inbetween the speedometer cable and the housing of the sm-465 4 spd manual transmission on my truck? The cable will screw directly to the transmission so this must have some purpose. It also says "made in usa" on it so it might be illegal...
It is made by by stewart warner. I've run the truck without it today and I can tell the speedometer is off some without it.

Ratio change box.

Reduction box.

The ratio is stamped on the box.

X2^^, or Ratio Adapters. Used with Large Tires or gear changes etc...
Speedometer Gear, Speedometer Gears, Ford, GM, Dodge 700R4 ratio adapter

speedo cable part
 

There are 4 screws holding this thing together. I assume it's just some gears inside. Can it be taken apart, cleaned and relubed without messing it up somehow?

nice site ssedan64
thanks for posting it

Not meaning to be rude, but if you didn't know what it was, I'd say you can't.
Anyway, why would you want to?

You can take them apart. Just go slow so both gears stay on one side. Some of those allow you to change the gears inside for different ratios. Some don't.
And not to be rude but you'd definetly want to take it apart to see what makes it tick. You'll never understand how it works if you don't take it apart. JMHO

All that is inside is two or three gears. As long as you don't lose the gears or get them mixed up, you should have no problem exploring the insides.