I recently posted about my 4x4 drive acting funny. I had a mecanic check it out, for the second time. He noticed I had a 3.21 on the rear, and the front was stock at 3.55. I currently have 35' tires with a 6 inch lift. He reccomended I upgrade the front and the rear too 4.56, due to the fact of the tire size. Or should I just change the rear back to 3.55. I do hate the fact my speedo is off by 20mph, and the lag i get. Please help. I really know nothing about this.

Will this decrease my highend,gasmilage etc

It's about 500.00 to change the rear to stock, our about 1100 to do a 4.56 all around.

 

your speed would be off by a percentage. i went from 265-70-17's to 34 1/2" tires on my truck and my speedo was off by about 10%. to correct the speedo i changed the plastic gear on the speed sensor which is on the transmission to a gear with 10% fewer teeth. the gear is available at the ford dealer for about $10.
i have 3.55 gears on my truck right now and it is gutless. i am currently in the process of aquiring a set of 4.56 gears for my truck too. it will take alot of pressure off the transmission and engine and use less fuel if there is any difference.
go for the 4.56's with 35" tires. the truck should rev at about 2200 rpm at 70 mph.

 

Do it!

 

go to a rear end shop not the dealer... if there is a track or something that holds races near u im sure the guys know a great fast place to do rear end work. it will be alot cheaper and way faster then the stealership.

 

"STEALERSHIP"

 

Cool thanks

 

A 3.21 and 3.55 at the same time? Funny. Go for the 4.56's. I will be regearing soon too.