Hey guys I have done some searching around on here and can't really find any answers on weither you guys recommend 3:73 or 3:55 gears. It will be for street 90% strip 1% and highway 9% lol I don't know if I will notice the difference on any or those applications. I'm mainly looking to run close to 110-120 in a race at WOT not in OD cause I have a AOD tranny.
We can work the math backwards to tell you the maximum gear.
Let's first assume, because it helps make the math easier, your redline is 6000 RPM, and that's what you want to hit 120MPH at.
Given that 6000 RPM is 100 RPS, and 120MPH is 2 MPM or 1/30 MPS ...
A stock 225/60R16 tire is nominally 26.60" diameter, 83.66" circumference.
An AOD in 3rd gear is 1:1.
Every second, your car will be travelling 1/30 mile, or approximately 176 feet. 176 feet is 2112 inches. Your tire will spin 25 times for that 1/30 mile. To get the tire to spin 25 times, while your engine spins 100 times, you'll need about a 4:1 ratio. So given all that, I'd opt for 3.73 rear gears. This will put you at about 5600 RPM at 120MPH.
Please correct for your car's actual rear tire circumference, your actual redline, and your desired RPM at 120MPH *grins* But that's what the math says.
RwP