How much does going from 33's to 35's on a ford f250 7.3 affect towing, mileage and towing power?

very little. Do you have a programmer or module that will let you recalibrate speedo? The power will still be there, the keeping the trans shifting at the correct time will help.

Depends on how much weight you are pulling. Not as much an issue on the 7.3 versus the 6.0 though. I have a 6.0 and run an Edge box to help put the power back that I lost from reducing the gear ratio. Remember stock trucks came with 31" tires.

MPG will go down if you go a lot wider but if you stay the same width or not much wider you should be fine.

I have a 01 Excursion with 325 65 18 (35x13.5) with a ton of other parts but the stock 373 gears and I don't drive easy and get 19.5-21 mpg, My son who is scared to f up my truck gets like 22-23 when he drives it. Got about 112k miles on it now.

I have an 02 F250 crew cab short bed with a DP tuner and stock tires and am only getting 17 mpg. How are you guys getting that mileage with bigger tires even? My truck is 4wd and has around 105000 miles.

The programmer can make your motor more power, but lowering your rpm's is the key. Putting on a larger does that. Too big can be just as bad though.

BigBoat 28 how many maps have you run on the DP tuner ? I know they are good and have a pretty much unlimited abilty for tuning you may want to try some other maps.

I'll try to remember everything I did to mine, Edge Juice with attiude I drive on 3rd setting witch is the "drive" setting, I get worse mpg on stock because of how I drive and only use tow when towing settings 4 and 5 are just for fun and the stop light grand prix. 4 inch Magna flow exh. from turbo back, bigger intercooler, AFE stage 2 air box, fluid damper,the trans is built to the hilt with a better converter, I need to find the build sheet on it, the old trans was fine but when I got done with the truck I didnt want the trans to blow up and I picked up 1-1.5 mpgs with the rebuild, On long trips it wouldnt matter but in the city with all the shifting is where it picked up the mpg. All fluids are syn, except for the eng oil I use the Rotella 15x40. Injectors were redone for better flow and hp but when your not on it helps the mpg. I have a wicked wheel and other little turbo mods, I am go to put a better one on with the intakes this summer. If you have a friend at Ford take it to him and put all the Ford Updates in the ECM, I unhooked my turner and had them load the updates, the tuner dosnt rewrite everything and sometime the changes depending on the car can be big. I don't know how much it did on my Excursion because I did it when I was doing a bunch of stuff, but when I did my Linc. LS it picked up almost 3 mpg and it drove and shifted much better. I know I am forgetting some stuff. Theres a ton of other crap I did but none to help MPG.

I dont know how it is the other guys but when I got my first PowerStroke I couldnt get $hit for MPG the truck was all stock and the way I drive didnt go well. I sold it to my best friend and got a Dually because I was towing more and started do mods for power but I was getting better mpg too. My old truck now has some mods that my friend did and it is getting better than I did out of it. Also the way you drive is all of it, I drive fast but dont boost real hard, if I do run it hard I would be lucky to get 10 mpg.

The setting I have are 40hp for towing, 80hp econo and towing up to 3-4000# and then 2 play settings of 120hp and140hp race. I got 16mpg before tuner and 17 now.

I know they say the key to mpg is partly rpm's. I've heard over 2000 rpm mph goesd down. So where does tire size hurt, 33 0r 35 or bigger? How many rpm are you guys turning at say 70mph with the 33's and 35's?

75mph is 1900 rpm in my truck. If I went any bigger on tires I would have to go to a 410 gear.