Tire size with 4.30 vs 3.73
 

Ordering F250 today and kinda torn between 3.73 and 4.30 axles. Lariat Ultimate with 6.2 and I want to run at least 34" but possible 35" tires. Heaviest load would be 9k fifth wheel very occasionally, and an extremely light flats fishing boat. Vast majority of time will be highway running with some city. With the 6.2 will 3.73 match this use best with tires that size?

I know everyone says to get the 4.30s but all those guys are towing heavy frequently. And IF I can find a 6.2 on a lot, it is typically in a XL-STX work truck with 245-75-17 little tires so driving that is not a good comparison. 3 dealers have looked at me like I was a moron for first wanting to order a gas engine, and second for wanting to order a 4.30 EL. Starting to get embarrassed a little to go to a dealer to talk about ordering a truck.

So will a 6.2 with 3.73 pull 34" or 35" tires adequately without being a total dog not having enough power to get out of it's own way? And be able to pull my 9k 5er occasionally? Also would like to be able to get at least 12 mpg on (by far) most usage on highway not towing anything up to 80 mph. Cant find any 6.2s on a lot with the 20" wheels and 34" tires to test drive which would answer all my questions. Oh yeah I am NOT going to buy another diesel, total overkill for my needs.

And yes I get it that a F150 would work perfectly fine for 98% of my daily driving, but I need to be able to pull that fifth wheel from job to job. Only reason for needing a F250 really. Any feedback on this super appreciated.

Put 35's on the 3.73's and your effective axle ratio is going to be about 3.30. I'm not sure I'd even want to drive empty with that ratio.

If you are worried about fuel consumption, over-sized tires are about the worst thing you can do. Lots more rotating mass.

IMO, get the 3.73's and keep the stock wheels.

First tell the dealer to go pound salt and order what you want, it's your money. If your going to put that tall of a tire order the 4.30 gears, you will be glade you did. I never took any crap from the dealer because I built mine on line and sent 5 of them the sheet for prices, the one I ordered from questioned the 4.30 gears and he was told if it didn't come with 4.30s I wouldn't take the truck.

Denny

4.30
 

Bigger tires and your towing. Both reasons to order the 4.30s. I just got my 2019 f350 4.30s and would never have bought with 3.73s. You will never regret the lower gears but you will regret 3.73s. Havent seen a post here saying man I shouldnt have bought the the 4.30s

9k.. even once a year.. with hills.. 4.30...

the truck with 3.73 and stock size wheels will do FINE.. till heavy and hills.. it can still do it..
most complain of the engine high rpms... the 6.2L loves rpms. owners do not..

but 9k.. hills.. and oversized wheels.. you are asking to be unhappy..

Test drove a truck with the 3:73's before ordering one with 4:30's. Towing or not, the 4:30's rock for my style of driving which is mostly around town with occasional highway use. Trip computer shows 14.2 average for the first 650 miles. I am a Ford guy and could not put myself back into a 10 speed truck so another F150 was out. I do not need a 250, just wanted one. The heaviest thing I plan to tow is a boat weighing about 5K.

If most of my driving was at 75 or higher and only towing light loads the 3:73s would of gotten more consideration.

I have the 3:73 gears in my F250 and tow a 10K fifth wheel with it, If you are going to get 35" tires you without a doubt want the 4:30 gears. I bought a set of stock 20 inch rims (34.6" tires) to try out and quickly went back to my original 17's (31.4" tires) because I could feel a big difference without towing anything. Good advise above.

As a side note, I am happy with the 3:73 gears/stock tires even pulling passes in 4th gear......But any heavier trailer or larger tires id be all over getting re-geared and maybe getting a F350 instead.

Thanks for replies ASAP. I did a little checking and for the stock 275-65-20 size, the 4.30s have an effective ratio of right around 3.87 which to me is just about perfect. So I could have the stock 20" wheels (or some Method 17" with some 35s or 285-75-17) and have just a slightly lower gear ratio than the 3.73s which should then be just about perfect. I can run Michelin 275-65-20s or really all the tire manufacturers make that size, and should get about as good fuel mileage as these trucks can get. Which if I was super worried about fuel mileage I would not even buy one of these trucks to start with.

Thanks guys.

After broke in my truck gets around 13.2mpg to 14.2 mixed highway and city 50/50. Towing goes from 7mpg in the mountains to 10mpg on the flats. I try to stay at 60mph pulling for reference

The 6.2 just plain works better with 373 cogs. Towing or not. I had a 2012 with 430s and enjoyed it. My 2017 has 373s and will walk all over the 12 model with the new tuning/tranny they use. I run 35s on both trucks and they do just fine with 373s but I only light tow. Both trucks get 15mpg

Done!
 

I just drove a 2019 with 3.73 and stock 18" wheels/tires and to me it seemed obvious that with 34" or 35" tires, the 4.30s would be perfect for the 6.2 IMHO. However 4.30s with smaller tires would not be great unless towing really heavy.

SO I just initiated an order. F250 Lariat Ultimate with 6.2 and 4.30 axles. Now waiting...

Running 4.88's with 37's. So very similar to a 4.56 with 35's. I tow heavy a half dozen times a year. I daily drive the truck. I really enjoy the set up. No way in hell would I consider ordering a truck with 3.73's knowing I was going with bigger tires. That actually seems foolish in a truck with a double overdrive transmission that likes to rev and weighs north of 7k. The guys working in sales at the dealerships are rarely the guys you want to take any mechanical recommendations from.

Agree. A lot of the sales people at the dealerships do not know the products AT ALL. Not much help to someone trying to make educated rational decisions before plunking down substantial funding on a truck. But that's the way it is most of the time unfortunately.

The really neat thing is I can swap out the 34s for a set of 35s and readily adjust effective ratios to right near the 3.73 ratio just with tire size. But I think it will be perfect like that and did not intend to go over a 35" tire size so the 4.30s should be just right. But the flexibility to adjust is there, where if I had 3.73s I could not do that at all.