i am getting new gears soon (4.10s). i was talking to the mech who is going to be doing the work, and he said the speedo can be taken care of with a "reluctor". when i search online i get lots of chevy links, but no ford links. is this just a chevy thing? or is this also applicable to a ford mustng. i dont want to get a computer unless i have to right now.

 

A reluctor on a '03 mustang? The computer handles all the speedo calibration. All you have to do is have the ECM flashed and have the gear setting changed from whatever the factory is to your 4.10's. Reluctors are usually old school. A reluctor is basically a circle with teeth on it that spins. There is usually a magnet involed and everytime a tooth spins past this magnet, it's recorded/transmitted by the stator assembly (the device that contains the magnet). This signal is sent to the computer or ignition module to adjust whatever it's supposed to. Usually found in older distributors but some trannies or rear diffs (chevy)

http://www.napaechlin.com/cpc2b.htm