69 mach 1 429 gearing - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

trevfildes · 03-19-2009, 09:17

Hi from the uk
Need to sort the rear end out,has C6 auto and at moment has 4.11 gears and at 45mph is doing 3000rpm does anyone know what the speed would be using either 3.00 or 3.50 gears at same revs.
Car has 400+hp so guess will still pull hard as at the moment just shreads tires and car is used as a wedding car,more interested in gas mileage than 1/4 mile,thanks.

1meanGT · 03-19-2009, 23:18

You do not mention tire diameter. Assuming that your tire diameter is 21 inches, a rear end ratio of 3.00 will deliver 2,160 RPM's and a 3.50 will deliver 2,556 RPM's.

If you want- there is a calculator at RICHMOND Street Performance Calculator that you can play with.

trevfildes · 03-20-2009, 02:58

Hi,thats great thanks for the link.