21 tooth driven gear

June 24, 2006, 01:19:57 AM

What rear gear ratio is most accurate for a speedometer 21 tooth driven gear and 8 tooth drive gear (as on 87 AOD TBird/Cougar?), combined with 225/60/15 tire/wheel set up? Still pondering the 3.27 - 3.45/3.55 - 3.73 gear choices without changing half the drivetrain to upgrade from a 2.73 traction-lok 7.5".

21 tooth driven gear

Reply #1 – June 28, 2006, 10:44:15 PM

You just have to go the next gear size up for your gears...i.e.-3.55's-21 tooth, 3.73's-23 tooth(as opposed to 21 for a 'Stang)

However, I just had 3.73's installed and there were out of 23 tooth gears so they popped in a 21 tooth(supposedly)...my speedometer is now perfectly calibrated to 3.08 gears. So somebody lied or they gave me more gear than I asked for(which I highly doubt).