Well I did some calling around today too fine part numbers and pricing on the 3.84:1 final drive gears. I can get the ring gear no problem. The final drive pinion gear purchase option has been changed by ford (according to the dealership). Now the only way to purchase the pinion gear is with a complete output shaft set - for 1000 dollars.
At that price the gas savings will never payoff.
Any suggestion, or does anyone have a 3.84 set they want to sell or trade for a 4.06:1 set?
