How many teeth should a 1st gear and final drive have from a 4.7 ratio?

my final drive has 66teeth and 1st gear has 42teeth

 

1st gear has nothing to do with your "final drive". Final drive ratio is determined by dividing the number of teeth on the differential ring gear by the number of teeth on the differential pinion gear [AKA countershaft].

B-series final drives break down as follows:

64 / 15 = 4.266
66 / 15 = 4.400
67 / 14 = 4.786

If your ring gear has 66 teeth, you have a 4.4:1 final drive ratio.


Modified by B20C5 Turbo at 11:27 PM 12/5/2006