That makes sense, and I'm glad to hear it since I always like the way larger tires look on an SD. Thanks!

 

With the proper tools, you can recalibrate the system with the new tiresize and the odometer will be right.
JL

 

I know off-road shops do this regularly, but is it something I can do at home? I'd rather not buy an expensive tool I'll only use once in my life. I mean, I've re-calibrated the older, gear-driven speedos by doing the math and buying another gear, but I have no idea how the electronic, sensor-driven speedo's do it. Any tips?

 

Only if you have Ford's electronic tools,or an equivalent.Pick a tiresize and stick with it. Then go pay one of the shops to do it,or make the investment on the tools.
JL

 

You used to be able to get 3.73, I'm not sure what year they changed but now the V10 comes with 4:10 std or 4:30 opt. I dont think 250/350 or 2wd/4wd changes that, just the v10 (5.4 you can still get 3.73).

IMO if you actually haul anything with a dually I'd look no less than 4:30. I think the only time 3.73's will actually help you is unloaded on the hwy. And just being a dually I would think to expect a slight mpg drop over a srw. Your turning a heavier axle, alot more tire on the road, and more wind resistance too. however your numbers do seem a little low, I'd suggest as others have said to give it a good tune up. Good luck

 

In my completely stock 2008 F350 4x4 SC SRW 4.10 with 25K miles I get 9.8-10.1 in city (stop lights and such, not counting traffic jams) and 13.4 - 14.0 on highway depending on speed, and topography.

 

comming back from up north i got 7.5 but my truck has a 10" lift and 38.5 tires