I have a 2002 F-150 Supercrew Lariat with the 5.4 L enging, 3.55 gears, 275/60-17 tires and wheels. I have the 3" flowmaster exhaust, 1715 superchip in performance tune, and air force one intake. Would it be beneficial to change to the 3.73 gears for quicker acceleration and how would it affect my gas mileage. Right now I get between 12.5-13 mpg on 93 octane gas. Thanks Jimmy

 

Your not going to gain much acceleration by installing a deeper gear. It will launch quicker, but the engine will top out sooner. Mileage will stay about the same. If you were putting on bigger wheels, then the 3.73's would help to get those wheels turning. Otherwise your not going to see much benefit from it.

 

I will be installing a set of 22" wheels and 305/40-22 tires. I notice that the Ford lightening has a 3.73. Would installing a larger throttle body give a noticeable performance gain? Thanks

 

you wont see much of a gain from changing out your throttle body you will gain alittle high end horses i will say like 5-10 hp if you port out the intake elbow to match the new throttle body, going from 3.55 to 3.73 will not make much of a difrence with those heavy rims and bigger tires i would suggest 4.10 for performance

 

3.55 to 3.73 is a waste of time because the difference is too small. 4.10s would be fine with either tire height. If performance is your goal, you should go with 4.56s with the 22's. When you get quicker gears, your "HIGHWAY" mpg will be reduced. I'm with bigtruck311 on the throttle body; port the elbow or forget it.