ive got a 700r4 with a 9 bolt 3.27 rear end if i were to put 3.73's or 3.90's in it what would be the easiest way to recalibrate the speedometer

 

If you put in 3.73s, you can change the speedometer gears in the transmission. Any ratio numerically higher than that and you'll have to use an external adapter.

 

im not all that fimilar with transmissions and the speedometer gear except when i had to change the cable, what kind of work goes into changing speedo gears and what sort or external adaptors exist

 

It depends if you can only replace the driven gear, or if you need to replace the drive gear as well. Changing the driven gear is a 2 minute job that you can do with a 10mm wrench without even jacking the car up. Replacing the drive gear is more involved. Check the tech article.

 

thanks, withe the driven gear what size/ratio or whatever it is would i need for whatever gear set i decide to go with, because i was reading somewhere that no body makes a driven gear to match with 373 or 390 and that my speedo would alwalys be off

 

You can only get speedometer gears to go as low as 3.73s, that's why you'd need an external adapter for anything numerically higher.

 

would the external adaptor be something that comes off the trans between the cable and trans, ive never heard of something like

 

Yes, that's exactly it.

 

These will help:

http://700r4.com/speedoCalc/speedocalc.shtml

http://www.transmissioncenter.net/sp...__va.htm#700r4

 

so how many teeth is my drive gear