My 2003 f-150 with the 4.6 has the 3.08 gears, I just put a set of 20 inch wheels with 285/50/20 tires on it. Would it help to go to 3.55 gears and if so how will this effect gas mileage?

 

I think that 20" wheels with a 3.08 is a pretty bad combination, As long as you are easy on the take offs you might not break anything. I would recomend a 3.73 rear end and you'll probably see an increase in your mpg, right now I think you are using a lot of gas just to get it rolling!

 

rockyj,

That sounds like the perfect combination to thoroughly dog out a truck. I agree with suvdrvr. Will 3.55's help???.....YES....Would 4.10s be better???......YES.

 

What would be the best gears to run 3.55's-3.73's-or 4.10's? How will these gears effect gas mileage?

 

This is just a personal opinion....With that tire height, I'd run 4.10's. You're mileage will be the same in the city, slightly less on the highway, and you'll think you got a new truck going from 3.08's.

 

Thank's for the help. I don't think I want to go as low as a 4.10, the lowest I'll probably go will be the 3.73 but still trying to decide between 3.73 and 3.55. Someone from Precision Gear and Sam's Off-Road have both told me to go to a 3.55 to get the truck back the way it was with the factory tires but if I wanted a little more torqe to go with the 3.73. I drive my truck about 100 miles a day, so I want a gear that will help gas mileage back to where it was.

 

i've got 3.55's on my truck and was looking to go up to some 4.10's here soon. so if you're looking to buy some gears i would happily speed up the process, just send me an offer (through email) and i'll get back with you.
guess going to 4.10's would be down not up.

 

hey does anyone know the rear end size of the 2004's? 10.25" or 8.8" or what? i have 3.73 gears now and when i get 35"s i want to put 4.56 but i dont know what part to buy, thanks.

 

how do you tell what gear ratio you have? is there a number on the differential?

 

usually you can tell by the axle code on the driver's side door sticker, if not there though there is a number on the diff. if you do a search on here for axle codes you'll find what your code corresponds to.

 

Thank's for all of your help. I decided to go with the 3.73's I ordered the gears and installation kit from Randy's Ring and Pinion, my mechanic is going to install them Monday.

 

You're Welcome ! Randy's is great and you'll love the change from 3.08 to 3.73. Good luck with your installation. Let us know if it makes you grin afterwards.

 

I got my truck back from the shop today! The 3.73's are a lot better than the 3.08's I also installed a Superchips Max Tuner 1715 today. Feels like a new truck! Thank all of you for your help.

 

I'm glad things worked out well. "new truck = "....Enjoy !

 

rockyj - what was the part # of the kit you ordered??

Also, approx. what did you pay for install?? (If you don't mind me asking??)