3.73 gears how fast am i going?

If you have 26.6" diameter tires (stock), and you had a 3.27 gear before (stock for an automatic), then:

When your speedo says 80 mph, you should be going about 73 mph.

If you want to figure out more rpm vs. speed things just do the math.

26.6" diameter wheels = 6.98 feet per revolution
5820 feet in a mile
60 minutes in an hour
5th gear in a 5 speed is .71 (I think)
OD in an automatic is .64 (I think)

So:

at 2000 rpm, you divide by .64 (OD) = 3125 driveshaft rpm
divide by your rear gear ratio 3125 / 3.73 = 837.8 wheel rpm
multiply 837.8 by 6.98 (feet per rev) = 5847.85 feet per min.
multiply by 60 (minutes in an hour) = 350871.3 feet per hour
divide by 5280 (feet in a mile) = 66.45 miles per hour.
 
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