Hey guys.......I have a 2011 F250 Crew Cab SB, 4WD Lariat with 6.2L and 3.73 E-locker. Running 5-Star tuner on it, helps with the throttle-lag and gets true WOT when you put the pedal down. Also has Add-A-Leaf in the rear to help reduce Sag (thanks Ford for softening up the rear suspension on the new SD's so much, ha ha).Stock 275/65-20 tires. When I traded in my last truck (08 6.4 Diesel, tired of the headaches) it was the only gasser I could find, the 4.30 axle is elusive unless you special order. I LOVE the truck. It is my DD to and from work maybe 8k miles a year, towing a light utility trailer (2000-3000#) around from time to time, but only towing our Camper 2-3 times a year (1000 miles per trip).It pulled our old trailer (298BHS Starcraft Aruba, 6830# dry) pretty well. Has to wind out a lot (5000+ RPMs) on long uphill stretches to hold 60-65mph and fuel mileage sucks, but it was otherwise A-OK getting up to speed safely, etc. I wished for the 4.30 but it was never a necessity, until NOW....We outgrew the old trailer and now have a 321 BHT Sierra which is 6.5 ft longer and weighs 9400# dry. It's like pulling a house compared to the old trailer. ProPride 3P on the way to address sway issues with the trailer, but I am stumped on the power. Once I have the trailer up to speed, the truck pulls it OK, but getting up to speed it really struggles.I can A) pay ~~$2500 and have the truck re-geared with a 4.30 gear set, which will undoubtably HELP the acceleration and hill-holding when loaded.......the question is, how MUCH will it help? I've searched dealers around to see if I can find a 4.30 equipped truck to tow this trailer with, and I can't find one....Option B) is either trade the truck in and buy a used diesel (and really risk getting someone else's problem again), or C) pony up another $15k to get into a new diesel, which I really don't WANT the maintenance, headaches, and don't want to pay for either;)Any thoughts on how much difference I'll see swapping these gears? FWIW I have watched the video on 5-Star tuning's website, which shows Mike towing a 10k trailer with his 6.2L, tuned, 4.30 truck, and it definitely pulls better than mine.........of course, real-world, seat-of-the pants, it's hard to put that into perspective.I realize, this isn't a race. I don't expect to pull 11k loaded 0-60 in 5 seconds. But, I want to be able to safely pull out, tow, and manage hills in the truck with my family without having to sweat it.Any thoughts appreciated.Thanks, Ben

unless you need lower than first, which isn't what you are asking about, 4:30 the engine will turn @ 200 rpm more per gear. overall gearing is @ the same if you run 1 gear lower than a 4:30. So your 3rd would be 4th in a truck with 4:30, 2nd equal to 3rd...etc.So, I don't think you will see the difference you expect.Are you over at FTE? seem like the same question over there?

I would assume the 4.30 will help you launch. But once cruising it may not be as much of a help unless you feel you are stuck between two gears. For the hills you are just going to have to reduce your expectations. 50/55 might be the new normal rather than 60/65 when climbing. If you plan to keep the truck the $2,500 is well worth it. If you do much 4wd consider a front Truetrac differential for an extra $500.

You will increase your engine RPM by 12.6%.That means if you were turning 2200 before you will now have to turn 2477RPM to achieve the same road speed.You should certainly be able to feel the difference but the question still remains if it's what you're looking for. I predict it'll be pretty close. Should reduce the amount of downshifts required for those smaller grades and that can be nothing but better for your tranny.

Towing with a 3.73 F250 6.2L, will a 4.30 axle help ??

Learjet
Explorer
Oct 07, 2013
Not sure what the graph shows, what we need it a comparison with all six gears of the tranny.

If you are going down the interstate in 6th gear (2nd overdrive) with 4:30?

Interstate 5th gear 3.73 (1st overdrive)

...etc.

I understand if you are just looking at the rear gearing in first, but what happens through the whole range.
Mike_Up
Explorer
Oct 07, 2013
Sport45 wrote:
wnjj wrote:

You picked one of the speeds where the 4.10 has just changed to next next higher gear. That's where it will have a disadvantage. The problem with your example is there are many more speeds where the 4.10 has the advantage so overall it is more favorable. My chart below will show those areas where the 3.73 is still pulling after the 4.10 shifts.

Will the 4.10 still have certain hill/weight combos where it performs more poorly than the 3.73? Yes, when you are between gears (as in just shifting up) you aren't able to get the engine up to its higher RPM HP.

The difference between available HP and HP demand is what provides acceleration. When you look at the chart from an RPM in each gear point of view, notice how for every point on the RPM range (the slopes are each gear), the 4.10 geared truck has a greater HP advantage because it's there when the HP demand is lower.

The peak of each RPM is 5000 (my choice) and the valleys are ~3000 for the 1-2 shift and ~3350 for the 2-3 shift based upon the 6-speed ratios I used.

Note: I don't expect these actual speeds to match any particular real truck but to simply illustrate the difference. I just used ~35mph for 5k rpm in 1st for the 3.73 truck and 300 ft-lbs flat across 3-5k rpm.

Interesting. So if you're on a hill that requires 250hp to maintain 55mph the 3.73 will let you drop a gear and do it, but the 4.10 gears rev out and limit you to 50mph.

I have 3.73 gears in my F-250 and would have preferred 4.10's. But Ford only allowed 3.73 and 4.30 at the time and I didn't want to go that low.

From the graph, I see the 4.30 axle doing better than the demand through out the graph. The 3.73 falls short of demand around 58 mph. However it does have ranges of 5 mph, here and there, that it does better than the 4.30. BUT the 4.30 does much better the majority of the time and always stays above the hp demand for the speed, that the 3.73 can't.
Sport45
Explorer II
Oct 06, 2013
wnjj wrote:

You picked one of the speeds where the 4.10 has just changed to next next higher gear. That's where it will have a disadvantage. The problem with your example is there are many more speeds where the 4.10 has the advantage so overall it is more favorable. My chart below will show those areas where the 3.73 is still pulling after the 4.10 shifts.

Will the 4.10 still have certain hill/weight combos where it performs more poorly than the 3.73? Yes, when you are between gears (as in just shifting up) you aren't able to get the engine up to its higher RPM HP.

The difference between available HP and HP demand is what provides acceleration. When you look at the chart from an RPM in each gear point of view, notice how for every point on the RPM range (the slopes are each gear), the 4.10 geared truck has a greater HP advantage because it's there when the HP demand is lower.

The peak of each RPM is 5000 (my choice) and the valleys are ~3000 for the 1-2 shift and ~3350 for the 2-3 shift based upon the 6-speed ratios I used.

Note: I don't expect these actual speeds to match any particular real truck but to simply illustrate the difference. I just used ~35mph for 5k rpm in 1st for the 3.73 truck and 300 ft-lbs flat across 3-5k rpm.

Interesting. So if you're on a hill that requires 250hp to maintain 55mph the 3.73 will let you drop a gear and do it, but the 4.10 gears rev out and limit you to 50mph.

I have 3.73 gears in my F-250 and would have preferred 4.10's. But Ford only allowed 3.73 and 4.30 at the time and I didn't want to go that low.
dodge_guy
Explorer II
Oct 06, 2013
nohurry wrote:
This thread has given me a headache :W

Seriously though, it has been good food for thought. All I really need to know is that the engineers that design these trucks say that if you opt for the lower gear ratio, your tow rating goes up. Not just for that reason, but I'm convinced the gearing gives more capability across all gears. Yes I can just run in 5th gear when cruising down a stretch of level highway and be close to the same, but what about all the other situations? Acceleration, and hill climbing/descending come to mind. If a person has the expendable income, I think it's worth it. If money's an issue, it should work fine as is for 2-3 tows a year.

Looks like you were able to read through all the BS and understand what a few of us were saying! good for you! now do what you feel comfortable doing and enjoy!
nohurry
Explorer
Oct 06, 2013
This thread has given me a headache :W

Seriously though, it has been good food for thought. All I really need to know is that the engineers that design these trucks say that if you opt for the lower gear ratio, your tow rating goes up. Not just for that reason, but I'm convinced the gearing gives more capability across all gears. Yes I can just run in 5th gear when cruising down a stretch of level highway and be close to the same, but what about all the other situations? Acceleration, and hill climbing/descending come to mind. If a person has the expendable income, I think it's worth it. If money's an issue, it should work fine as is for 2-3 tows a year.
Mike_Up
Explorer
Oct 05, 2013
Grit dog wrote:
My 6.2/3.73 is not much of a pulling machine. Honestly doesn't pull any better than my '11 5.0 f150.
I don't think the gear swap will make $2500 worth of difference. You'll still wind it out on every climb just a couple hundred rpms at climbing speed.

The 6.2L in an F250 has a poor HP and Torque to weight ratio. A 5.0L in a F150 will definitely feel much stronger. Plus the 6.2L is detuned for the F250, I have no idea why but the torque curve looks no better than the better tuned F150 6.2L.

If the need is there for a big trailer, get the diesel. If not, keep the trailer size reasonable and keep the gasser. If you plan on living in it, I'd get the diesel for sure. For recreation, no way, go smaller with a gasser is what I'd recommend. I'm not a fan of diesel either with all the problems and maintenance expense.

Since the need to go larger is there, I would put that $2,500 towards a diesel instead of gearing. To much money for what was probably only a $200 option.

I've driven 5.0L F150 with the 3.55 and 3.73 axles. While a difference, it's not earth shattering. I wouldn't think that a 4.10 would be a large enough difference to make it worth the expense.
wnjj
Explorer II
Oct 05, 2013
RCMAN46 wrote:
I used my 05 Duramax with the Allison 1000 for my example. The 05 has a peak hp at 3000 rpm and peak torque at 1600 rpm. These would be ideal shift points. Max rpm is 3250 for the 05 Duramax.
I assumed 30 inch tires and a 3.08 rear end for one case and same tires and a 4.10 rear end for the second case. I will accelerate from 40 to 65 mph. A typical speed change when getting on a freeway and sometimes passing a slow truck when hauling my 5th wheel.

With the 3.08 I would be in 3rd gear going 40 mph at 1956 rpm and accelerate to 65 mph where I would be turning 3162 rpm.

Now with the 4.10 I would be in 4th gear going 40 mph at 1837 rpm and accelerate to 65 mph where I would be turning 2935 rpm.

Interesting the 3.08 gives me a change of 1216 rpm and the 4.1 gives me a change of 1148 rpm. Almost the same except the 3.08 is greater and Carecraft claims this will result in a shorter acceleration time.

You picked one of the speeds where the 4.10 has just changed to next next higher gear. That's where it will have a disadvantage. The problem with your example is there are many more speeds where the 4.10 has the advantage so overall it is more favorable. My chart below will show those areas where the 3.73 is still pulling after the 4.10 shifts.

Will the 4.10 still have certain hill/weight combos where it performs more poorly than the 3.73? Yes, when you are between gears (as in just shifting up) you aren't able to get the engine up to its higher RPM HP.

The difference between available HP and HP demand is what provides acceleration. When you look at the chart from an RPM in each gear point of view, notice how for every point on the RPM range (the slopes are each gear), the 4.10 geared truck has a greater HP advantage because it's there when the HP demand is lower.

The peak of each RPM is 5000 (my choice) and the valleys are ~3000 for the 1-2 shift and ~3350 for the 2-3 shift based upon the 6-speed ratios I used.

Note: I don't expect these actual speeds to match any particular real truck but to simply illustrate the difference. I just used ~35mph for 5k rpm in 1st for the 3.73 truck and 300 ft-lbs flat across 3-5k rpm.

To exaggerate the point I changed the 4.10 to a 10.0 which allows it to use all 6 gears. Notice how much more area there is between the available and demand HP lines. That is "extra" power for accelerating. The other interesting thing is that the higher gears are closer together which would also favor a lower axle ratio working better.
RCMAN46
Explorer
Oct 05, 2013
Carecraft wrote wrote:

There is a major problem with the Carecraft example. I shift my gears by the rpm the engine is going and not by the vehicle speed.
He assumed in both cases the car was in the same gear. He did not use the transmission for what it is intended.

Here is a neat site to use to calculate rpm's vehicle speeds etc with different transmissions and gear ratios.

http://www.grimmjeeper.com/gears.html

I used my 05 Duramax with the Allison 1000 for my example. The 05 has a peak hp at 3000 rpm and peak torque at 1600 rpm. These would be ideal shift points. Max rpm is 3250 for the 05 Duramax.
I assumed 30 inch tires and a 3.08 rear end for one case and same tires and a 4.10 rear end for the second case. I will accelerate from 40 to 65 mph. A typical speed change when getting on a freeway and sometimes passing a slow truck when hauling my 5th wheel.

With the 3.08 I would be in 3rd gear going 40 mph at 1956 rpm and accelerate to 65 mph where I would be turning 3162 rpm.

Now with the 4.10 I would be in 4th gear going 40 mph at 1837 rpm and accelerate to 65 mph where I would be turning 2935 rpm.

Interesting the 3.08 gives me a change of 1216 rpm and the 4.1 gives me a change of 1148 rpm. Almost the same except the 3.08 is greater and Carecraft claims this will result in a shorter acceleration time.

In almost every post in this topic the transmission is not taken into account. Combustion engines have a transmission to keep the engine in its power band if used properly.

In my example my 05 Duramax would perform almost the same with both rear ends with the exception when both are in 1 st gear or both in 5th gear. But if the transmission is allowed to do its job performance in vehicle speeds between 25 and 90 mph will almost be the same.
noteven
Explorer III
Oct 05, 2013
Learjet wrote:
06Fargo wrote:
:h

4.3 x 400lbs-ft at 3000 rpm at the prop shaft = 1720lbs-ft to the center of the drive wheels...

3.73 x 400lbs-ft at 3000 rpm at the prop shaft = 1492lbs-ft to the center of the drive wheels...

I think the 1720 one pulls harder on a trailer hitch

wrong, you are not going the same mph in your example. IF you are going the same speed then your transmission in the 4.30 is in a higher gear. thus the overall gearing is the same.

Rework your example at 40 mph, then get back to us ;)

I believe the OP's question around gearing was whether changing to a lower ratio would give better towing performance (acceleration, climbing etc), not what rpm = what mph.
noteven
Explorer III
Oct 05, 2013
wnjj wrote:
You have to view the gearing change while considering RPM and MPH. That takes into account the amount of HP available and required at each speed.

Carcraft has a nice article that contained this paragraph:

Carcraft wrote:
Here's a reason low gears can be beneficial to dragstrip performance that you've probably never considered. Assume that a car is in a 1:1 trans ratio, has 26-inch-tall tires and 3.08:1 axle gears. When accelerating from 50 to 70 mph, engine speed increases by about 800 rpm. Put 4.10:1 gears in the same car, and engine speed increases by 1060 rpm-the difference is 40 rpm per mph with the 3.08s versus 53 rpm per mph for the 4.10s. The greater rate of rpm increase versus road speed provides greater acceleration. Since horsepower increases as engine rpm increases (up to the point when the torque curve drops off at a greater rate than engine rpm increase), the engine is able to overcome loads more easily with lower gears than with higher gears. This helps not only in acceleration but in maintaining road speed under a load such as when climbing a steep grade.

I realize this is about drag racing but pulling hills is about getting the most out of your engine and gearing just like the last sentence suggests.

I actually plotted available HP versus MPH throughout 1st through 3rd gear with both rear axle ratios up to 70mph, shifting each at 5000 rpm. I also plotted an assumed linear increase in demand HP on the same graph. You can see where the lower geared truck HP climbs away from the demand HP more quickly in each gear. I used an estimate of wheel size and assumed a flag torque curve from 3000 to 5000 which is reasonable along with the actual 6-speed ratios. I can try to post a picture if anyone's interested.

I would be interested in a picture.