Picked up a 2002 F-250 5.4 4x4 Super Single Cab with 6'9" bed about 2 years ago. The truck was lifted by the previous owner and it has had 35" tires since about a week after I picked it up. The truck has 3.73 gearing and DOES NOT have LSD. I have a tuner on it and opened up the exhaust, but did not put in a new intake. I drive it very little and use it as a farm truck. I rarely even take it on the highway, but probably due to it being so sluggish. One reason I bought gas over diesel is that I only run it about 10 minutes to work or 15 minutes to property I own. I do pull motorcycles on my dual axle trailer, but that is even rare. Most of my use is loading it with tools and something like dirt, aggregate or mulch and driving out to do some work.

I want to regear the vehicle and it seems like 4.56 or 4.88 is the best way to go...leaning to 4.88. I'd like to give it some extra grunt and go and, hopefully, get some better gas mileage. I currently get 9 mpg at best. Anyone have a similar setup and comments?

If I'm regearing, it would be a great time to put in LSD or a locker...probably a locker. What are the locker options for my truck?

In addition to extra grunt and gas mileage, I want it to be capable when the road gets loose, muddy, snowy.

The truck has no rust at all and has 142k miles on it. It was a Florida truck, so the clear coat is fried and some of the exterior rubber is dried out. I plan to keep the truck for a long time. When I bought it, I had just about everything done to it to make sure it was in perfect running order, so I also have money into it.

Thank you for all your advice!

 

Just keep in mind that the lower the gears, the smaller the pinion. You start getting down there to 4.88 and that pinion is much smaller and weaker that a 3.73 pinion. Not that a 5.4 is likely to break it, but it's something to keep in mind. I like lockers over LS, but a good working LS is better than open diff. Most 350s we see in TX have 3.73 with LS so I guess you didn't luck out. The LS clutches are good for 200k unless you do a lot of wheelspin, which wears them. So that 200k is really only street use. I have 260k on my 02 SD and the clutches still work.

 

Perhaps I can give you a starting point for comparison. I have a 2004 F150 with about 64k on the odometer which I bought new. It has the 3-valve 5.4 engine and a 4-speed automatic, short bed and 3.55 limited slip rear gears. It is box-stock. The only non-Ford item on it is a Wal-Mart battery. Ok, and the tires, but they are OEM size. The truck has lived its entire life south of I-20; first in Mississippi and now in deep East Texas. I have driven it to both coasts and to the Gulf of Mexico, so it's no wallflower. It just doesn't go often. Average mileage, according to the onboard wizardry is around 13.something empty and around 10 towing. It turns about 2k RPM with the cruise set on 75 MPH. Back in the days when a transmissions top gear was 1:1, you could figure a 4:10 rear would give you 2:1 speedo to tach (2000 RPM, expressed as 20 on the dial would give you 40 MPH, 3000 (30) 60). Approximately.
Now the killer; more grunt and better mileage are almost always at the opposite ends of the performance spectrum, at least as far as normal budgets are concerned. More grunt takes more gas, whether you achieve it through gears or horsepower. Better mileage almost always comes at the expense of performance (grunt). (Always is a never word and I never say never)
Good luck with your choices.

 

re-gear, unless YOU can do it.. a 4x4 is $ 2,500 and up..

4.88 or forget it... tall tires are a bad thing for a "Working" truck.

5.4L a good motor.. but NOT a working horse.

my opinion.

 

My vote would be 4.88 gears with a Detroit locker in the rear, and a Truetrac in the front.

 

If you go with 4.56 gears, you'll end up with an effective ratio of 4.10. This is perfect for the truck that tows occasionally, but mainly cruises around town and the freeway.

If you go with 4.88 gears, you'll end up with an effective ratio of 4.30 which is perfect for a truck that works and runs around the property

 

I vote for 4.88's and a detroit locker in the rear. If you want something in the front I agree with the truetrac, but just gears and a detroit is already going to be $ and should be plenty adequate.

 

 

I wouldn't worry about the 4.88 pinion being smaller, the Dana 60 and Ford 10.5 have large enough gear sets to where that's not really an issue. It's more of a problem on the smaller Jeep axles I went with 4.56s instead of 4.88s on my Jeep for that reason.

 

Great info guys! Thank you for all the comments. 4.88 is where I was thinking, and you seem to agree as a group. The locker in the back would be a huge performance gain, so I think I will leave it at that. I have a local guy who did a Jeep for me and he does them inexpensively. I will contact him and keep y'all posted. Again...thank you!