Does anyone know why Ford changed the rear gears on the F150 to 355's from 373's when the 20 inch tires are added?

 

You would think it would be the other way around.

 

No kidding

 

i got axle code 19 and 20 inch rims and i got the rpms of a 3.73. people say 3.55 are kind of doggish and i don't see that on regular driving but i do when i'm trying to merge onto highways and trying to pass without punching.

i'm gonna look into 4.10 after my deployment!

 

I would say it is due to the tire size. the overall diameter is smaller then that of the 18" wheels/tires. You end up with about the same ratio as the 18's with 3.73's. I figured it out a while back and you would be 50rpm lower with that tire/gear ratio then that of the 18's with 3.73's. I think a 4.10 gear would be much more ideal.