We have a 7.3 superduty. We have lifted it 4:" and put 35 inch tires on it. We have read in lots of magazines that we need to change our gears from 3.73 to 4.10.

My question is will it affect the truck if we do not change the gears?? Will it change our fuel (mileage)

 

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You know this is something I have been playing around with for sometime now. Not that I will be much help to you LOL. I have the 4.10 in a 95 MY PSD, currently I have the 305's which are 33" tires and looking to put the 35's on her. From what I have now with the 33's and its ability to pull really well, I still tach pretty high on the road. I have the E4OD tranny which makes some difference too but in OD locked .78 gear ratio from the final drive of the tranny to the 4.10's I tach at 2300 running 70 mph. Which has given me 16-19 MPG on the highway.

Now I am after a little better fuel mileage as think its in the truck as she is now with 35's. I have this figured to put the rear ratio running the 35's to compaired to my 33's now with 3.90 gears, which I think I can live with that now that I don't pull the 30K + loads on the gooseneck I use to.

Now in your situation with the 3.54 and to go to 35's I would figure long as you don't tow you would be fine. I wouldn't be surprized to see highway speeds around 1500 RPM's though which I would think may bring your fuel mileage down somewhat if it does. Not at all sure of that though, so maybe someone here has this setup that will share with us his or her fuel mileage and performance.

Your truck now have any other mods to her? This and what tranny your running would help guys here to figure what you can expect to see hopefully. Welcome to the forum here too...

 

I just lifted my 2002 F350 4x4 CC SRW 4" and put 35" tires on. I can tell a difference in my acceleration. Going to 4.56 gears will put the rpm back to where it was with the 3.73's and stock tires.

 

As was mentioned, if you dont really tow anything you will be fine, and on the highway, your revs will be lower which will save fuel anyway. Depending on the width of the tire however, you will see a decrease in mileage. I ran 41" Michelin military tires in my F350 with 3.55s before I regeared to 5.38s, and the thing sipped the fuel like a miser, but these were relatively narrow tires for their height. What plans do you have for the truck, towing? DD?

 

Have you changed the gears???

 

In my opinion changing from a 3.73 to a 4.10 isn't really worth the effort or the expense. Those ratio's are too close together for me to bother with. If you wan't to restore the final drive ratio to what it was with stock tires a 4.30 gearset will get you the closest. The PSD has more than enough torque to pull 35's without any problems with the stock gearing. If you have 4wabs you may need something like the Superlift Truspeed to get the anti-locks working right.

 

How is your truck mileage since you changed the gears????