Guys,
Since I can't actually buy a truck yet all I can do is read about them and what you guys are doing with yours. That has led me across this info which I've found very useful in the axle ratio decision:

Understanding Axle Ratios | Pro Pickup

If I could summarize, a 4.30 may not be that bad, or even noticeable for your fuel mileage. It all depends on usage, both driver habits and if you tow.

In a nutshell, the mpg gains of a 3.73 are for unloaded, highway driving. The article states that there isn't a gain to be seen in city driving.

If you do lots of highway, unloaded driving (and I mean lots) then the 3.73 seems it would work best for you - if you are after mileage.

If your driving is fairly evenly mixed, then you may not even see a difference between the two (combined city / highway).

Now comes the towing question. Tow ratings aside, what I gather from the article is that the 4.30 will give better towing performance every time through the gears as it just gives the engine more torque at the wheels

Now let's compare the two axle ratios in the 6R140 tranny - specifically 5th and 6th gears. There have been many comments between here and rv.net that 5th w/ 3.73 is roughly equal to 6th w/ 4.30. Cranking the numbers through excel that seems true to me. I was in one of those enginerd modes and wanted to see where my old 4R100 landed compared to the 6R140 and then got crazy and compared the six speed 5/6 gears between axle ratios. Here's a screen shot:



It's not exact as I had to guess on tire diameters but seems close. About a 200 rpm difference between 5th in 3.73 and 6th in 4.30.

So my opinion - and just from a guy who ran some numbers and has not actually driven or towed these things - the 4.30 is what I should have. My truck now does mostly towing, and if it's not it's mixed driving. The next truck would be doing the same. Highway trips are with the trailer. I don't think I would see any unloaded mileage gain with the 3.73.

Hope that helps someone ... maybe worth a sticky?

GC

 

I have a 2013 F350 DRW 6.2 with the 4:30's and I think the tire size is 31.8 or something close to that. I traded in my '08 F350 V10 SRW with 4:30's and 34.2 inch tall tires. My RPM's in both trucks are exactly the same at 70MPH, 2100RPM. I think my same truck with 3:73's would be constantly down shifting and would drive me nuts. All I have to do is lock out 6th when towing on any kind of hill and on flat roads just let the trans do it's thing.

 

I believe the engineer from Ford who was on here back in 2010 when the 6.2 was released recommend using 4.30's if towing over 10k, anything under he said the 3.73's were fine. Even on that artice the guy recommended 3.73s for towing heavy and 4.10's for trucks with over size tires which would bring the ratio back down to abt 3.73 anyway. At the end of the day I guess it is buy what you are comfortable with as the gear debate is about the same as arguing about diesel vs gas. Of course we all know the oil burner is better same with 4.30's. I pulled my 34 1/2 ft V-lite the other day and was blown away by how hard the SD pulls with 3.73's, nothing at all like my Hemi Dodge was with the same gears so I see no reason to doubt the Ford engineers recommendation as my TT weighs abt 8500.

 

GC I ran the rpm numbers the same way before I made the decision to order my truck. I used 60 mph for my base speed and ran the rpms for my 2000 with 215/85/16 tires 4.30 gears against the 2013 with 245/75/17 tires, I figured 3.73, 4.30, 4.56 and 4.88 gears. I wanted the rpms in the new truck higher in 4th and 5th than my 2000 because the 6.2 makes its power at a higher rpm, with 4.30 gears it came out the 6.2 was 313 more in 4th compared to the 2000 in 3rd and 342 in 5th over 4th in the 2000, I also figured 4.56 and 4.88 just in case.

I was worried about engine noise at the higher rpms with the 6.2 but after the few miles I have put on it all I can say is Ford did a great job on sound deadening this thing ,

Denny

 

That's great to know Denny - thanks for the "peer review" Always great when we can banter this stuff around to figure out.

Not apples to apples but it sure seems to me that the 6.2 is nice and quiet - I was running errands yesterday and walked past one in the parking lot. After staring for awhile I realized #1 the engine was running and #2 someone was in it! He was probably wondering where the stalker came from....

GC

 

Thanks for taking the time to do that GC, I'm in the same situation as you, and your charts are great food for thought. If all goes according to plan I should be ordering mine right after the first of the year. My travel trailers GVWR is only 7600 lbs, so the 3:73's would probably work fine. I can't help but think though that with the 4:30's it would be happier because it would be closer to peak. So unless I see a deal on the lot that I can't refuse, I'll order and go with the 4:30's. I'm not at all phobic about letting these Ford V8s rev. I've towed with my 5.4 for ten years now and she still screams up the hills just fine. Gettin up there in miles though, and it's just time to upgrade. I'm really gonna miss her.

 

i seen some where someone mentioned about a 7 to 800 rpm difference in 373 s to 430s on the same size tire . so my truck at 50 mph does about 1200 rpm so that same set up with 430s would be about 2000 with the steeper gears. id say if its alot of just transportation and occasional haul and tow go 373 of you tow alot and haul alot go 430

 

Go 4.10s at a minimum. If you have the money to buy a truck of this size then the marginal amount of $$$ you save on fuel will not out weigh the better power and towing experience that the 4.10 and 4.30 gears will give you. I've always bought my trucks off the lot so all I have been used to was the 3.73 gears. With my 2013 I ordered it built with the 4.30 and DAMN!! IT Accelerates so much harder. Nothing like being able to hold 6th gear going up a steep hill like its not even there.

 

If I had ordered I would have ordered the 4.30 since I don't drive more the 12 miles to work and not at high speeds. That said, I am very happy with the 3.73 and the 6 speed transmisson. I just lock out 6 and it works great. The engine makes a lot less noise at higher RPM than my Nissan Titan did. Getting ready for some longer trips soon

 

It seems that most of the guys buying 6.2's and wanting 4.30 gears are having to place a special order. And I'm ASSUMING that doing so costs more than buying what's in stock, on the lot (though I've never purchased a brand new vehicle so maybe that's a bad assumption...).

Question: would it be more cheaper to buy a 3.73 truck, then have Ford do a 4.30 swap (to preserve the power train warranty)?

 

I couldn't get any of the dealers to sell me a truck on their lot for $750 UNDER invoice but I was able to order one for that price very easily. Also when you consider that you are getting the exact truck you want and not paying for any options you don't want, it
nded up being A LOT cheaper to order my truck. The wait, on the other hand, really sucked haha

 

It doesn't cost anymore to order than to buy what's on the lot. Like ccstp said, the only thing is costs is your time (waiting on it).

 

When I ordered my truck I kick myself now for not ordering it with the 4.30's it was only a $300 option at that time. So after having it a month I called the Ford dealer to see what it would cost to have them change it and they came back with $3500 price tag to do that. Needless to say I still am driving around with the 3.73 2 yrs later LOL. I just wish I would have educated myself alittle better before I ordered.

 

You're welcome rimfire - and I'm with you - my thinking is 4.30 for my 10k 5er and what I use the truck for. I haven't driven one back to back yet but I venture a guess that a revving 6.2 in a new SD is quieter than my 7.3 chugging at 2k Not to mention all these comments I hear about the 6.2 sounding like a Mustang gettin on it...

If my calcs are correct, the difference 3.73 vs 4.30 in 6th with these trucks is around 300rpm...

I've often wondered what the axle swap would cost. I will have to buy used when the time comes and finding a 4.30 truck - needle in the haystack. But I can wait and shop around. I think. I wonder what indy shops would charge for that.

 

Just for reference on my DRW with 245/75/17 tires at 60 mph in 4th the rpm is 3167, 5th 2368 and 6th is 1845. The little I've driven it so far it looks like my calculations are close or should I say the tachometer is close.

Denny