I have a 2003 f-150 fx4 offroad model with the 5.4L V8. I am getting ready to put a 6 inch lift on it with 35" tires on 17" wheels. I don't know excalty what the stock gears are in the truck and I was wanting to know when i put the bigger tires on it should i stay with the stock gears or should I go bigger on the gears. This is also my daily driver so i need to know which way it would be better for gas mileage but if i have to scarifice mileage for less stress on the motor and tranny then i will do it. If i need to go bigger what gear should i go with? 35" or 36" tires are the biggest i will ever put on there. So i need yalls feedback on this. Thanks for the help

 

Your stock gears with the 5.4L fx4 are most likely 3.73's. If this is the case, I would buy a programmer for the truck and see if you like how it rides. You are putting more strain on the motor and tranny, but 3.73's can handle the load you are putting on the truck. If 35's are the largest you will go, then you should be fine. If you tow alot, or get sick of the lugging around town, I would go with a 4.10 or 4.56 ratio. 4.56 will be a blast and make the truck really fun to drive, but highway mpgs will go down. 4.10's will get your truck back in your powerband, reduce strain, and get you back to stock. Choose this option if mpgs are your #1 priority. choose 4.56's if you want performance. The reason I suggest driving the truck without new gears/ with programmer is that you may realize that you don't mind the performance and gearing is an expensive and precise job.

If you have 3.55's, go with 4.10's or 4.56's immediately.

My suggestion is to go 4.56. I have 4.88 to gear for future 38's and this thing is an absolute rocket!

 

4.56's if you still want that thing to move bottom end, those are big tires, and the highway revs will still be low, might even be similar to the stock gearing now. And the truck will still have "*****" around town and criusing.

 

I have done pretty much the same thing as tnsilverfx4. Except I put on the 4.56's in the rear only to try it out and decided to go with 4.88s since i may go with 37s or 38s in the future.

The 4.56's were perfect with the 35's though.

You will see a lot of downshifting going even up small hills on the highway they way you are now. 4.56 pretty much puts it back to stock. maybe a little lower geared but not much.

My MPG got better with the 4.56's compared to the 3.73's with my 35's on.

by the way i only put about 500 miles on the 4.56's then took them out.

they are for sale. cheap. let me know if your interested. there is a pic of them in my gallery

 

4.10s are a wasted of money with 35s, eslecially if you have 3.73 now.

You're gonna want to consider 4.56 or 4.88 with tires that large.

 

ya people told me that too when i was looking. 4.10's and 3.73's aren't that far apart so it's not worth even doing.

 

Hi guys thanks for the help i will probably go with 4.56 then