Hey all I am having 3.73's installed very shortly and was wondering what I need to do to keep the speedometer accurate. Do I need a speedo drive gear, or just a speedo gear? I appreciate any help thanks.
To get the speedometer to be VERY close, you need to pull the tailshaft off of the trans and replace the 8-tooth gear with a yellow 7-tooth Fox body gear. After you change that, you can use a 21-tooth speedometer gear, and the speedometer should read accurately up until about 70 MPH. I've found that mine reads either fast or slow (can't remember) 1 MPH at 70 and about 3 at 100.
I use to have 21 tooth gear with stock 8 tooth geardrive but when I rebuild my tranny I change to 6 tooth gear drive and 18 tooth gear because if I ever go with lower gears like 4.10 ,with stock 8 tooth geardrive you cant find like 23 tooth so if you open tranny change geardrive with 6T
I need to get mine calibrated with new speedo gears.
Right now, I have a piece of paper on my instrument panel that says to go 10 read 12 and so on. I just worked out every 10 mile per hour speed and what it will actually read on my speedometer.
EDIT: Here is a ROUGH conversion with 3.73's from 3.08's.