speedometer gear changing ?'s

[98tadriver]

my car has a 3.27 9 bolt rear under it right now. it used to have a 2.73 rear.
my original 700R4 is coming out, and im putting another 700R4.

can i just change the speedometer gear out or do i have to change the driven gear as well? who here has done this before? all help is appreciated. thanks!

[Fast92RS]

I have done it. I did it when I switched from 273 to 323. I just swicthed the gear on the speed sensor. It wasnt as accurate but it was real close, but when I had my trans rebuilt I swaped both gears to get the proper calibration. Is yours mechanical speedo or electronic?
Here is a website for you for gears and more info. This is wear I bought my gears from.
http://www.transmissioncenter.net/speedometer_calibration_______va.htm

also here is a calculator http://www.bgsoflex.com/speedo1.html

[WildBillyT]

Don't forget to take your tires into consideration as well.

[IROCdan330]

ron...if you have a mechanical speedo:

you will most likely need to change your drive/driven gear, both in the tailshaft of the trans.

www.700r4.com has got a speedo calculator to know which combo you need.

and like WildBillyT said, tire size is of concern for it to be accurate, and that calculator uses it.

Keep in mind, if you go over a certain tooth (39) driven gear, you will need a 40-45 tooth carrier, sort of like a 2 series and 3 series carrier in a diff.

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

gears/carriers:
http://www.bowtieoverdrives.com/catalog/catalog.php?Action=GETSUBCAT&CATID=DA2

[HardcoreZ28]

Changing both gears isn't all that difficult. The drive gear requires you to remove the driveshaft and the tailshaft from the tranny but it's not all that difficult. Once you open it up you'll immediately see how to change it.

[98tadriver]

thanks for the info fellas! i figured id changed this before i put the transmission in the car. that calculator thing is awesome. it doesnt get any easier than that!