I am stuck... I am thinking of buying a new 350/450 and the only basic difference is the rear end ratio which is 3.73 vs. 4.30. I am pulling a 40RP on an aluminum Myco so loaded maybe 15K. I am planning on putting a leveling / lift on the truck with 22.5's and wondered if the 3.73 gear would be enough. All things being equal does the mileage difference make up for giving up the gear ratio. I usually pull to poker runs 4-5 times a year and I run 75-78 mph so has anyone done the bigger wheels on a 350 and been happy with the pulling capability.

The 450 will turn much tighter if that matters

Increasing tire size in the range you are talking generally/approximately costs you one gear ratio. So, if you go a size bigger on tires with the 4.30; you will be back to roughly a 4.10.

IMHO with that load, I would go with the 450 and the 4.30 gear.

What kind of mods will you do to increase power? If you are going to do things to make it a beast, you might be happy enough with the 3.73 ratio in the F350. How strong is the ford transmission nowadays anyway? Is a 4.10 ratio available? The F450 at 78 mph is going to be turning some big R's.

450's now come with 17's the same as the 350. I am not sure of the differences as well.

I have an 11 450 and couldn't be happier. The turning is awesome over the 350 and with the new 6 speed tranny R's are not that big of an issue they really won't be with 22.5's.

Good to know. What R's do you turn at highway speeds?

really don't want to do any engine mods because of warranty and the thing turns 800+ ft/lbs of torque already. That's as much as my C7 in my F650 now and its an animal so all I really want to do is add wheels but who know? May end up with a Sport Chassis before I get done

F350, I pulled a 44MTI with 08 F450 which it pulled great but the mileage was horrible because of the gear ratio and RPM's. I now have a GMC 350, and it pull almost the same but twice the mileage. The newer trucks are rated higher than they were in 08 and it shows.
Also I am not a Ford guy but I don't think the new Ford 450's have the turning ratius of the older ones which sux because I do miss that.

I had the 08 450 and now the 11 the new one will still out turn a 350 but I do have to agree I think the 08 turned sharper. I was blown aways the first time I drove the 08 coming from a 250 and going to a 450 that thing would out turn it by a long shot.