if i change my rear end from my 2.73's to a 4th gen 3.73's, and i going to have to recalibrate my speedo?
if so, how would one accomplish that?

 

Inside your tailshaft there is two different gears. One goes on in your actual tailshaft and is attached to the speedo cable hookup. The other is actually attached to the transmission shaft itself.

When you do a gear swap you will need to change those two gears also. This will keep your speedo correct. Without these your speedo will be way off.

 

i know i'm kind of a rookie.. but i have no idea what you're talking about... what's a tail shaft? and where are these gears? any pics?

 

The tailshaft comes off the backside of the transmission. Under it are the gears. Try doing a search for "speedo gears" you should be able to find more info than you can shake a stick at.