I know this has probably been hashed out before, but want some real life data if available.
I am pulling a 9000 lbs 5er with the truck listed in my signature below.
I have towed into the mountains (Beartooths and Big Horns) last year, and it did OK, but I did not have the 5 star or the Y pipe at that time.

I am contemplating either re gearing to 4.10 or 4.30, or possibly buying a Diesel.

How much difference will it make with 4.30 compared to 3.73 gears, for pulling power, staying in overdrive with the trailer and mpg?

I currently get 8-9 mpg towing at 65mph in OD, and 7-8 mpg at 65 in drive (usually hilly or windy). What have people seen with the 4.30.

I get 12-14.5 empty depending on speed. Thanks

 

You will probably get about the same MPG but with much less strain on your drivetrain. BUT, if I were you, I would swap to at least 4.56:1 instead of just 4.1 or 4.3.

Only thing I can compare this to is with my other vehicle. I have a 2000 Durango with the 5.9 and it had 3.55:1 gears. I swapped to 4.56:1 as I regularly tow about 7,000 lbs with it. The difference is night and day and the mileage actually went UP while towing and stayed the same for empty in-town driving. I did lose one MPG on empty hwy driving.

I have a 2000 Excursion with the 4.3 gears and have actually thought about swapping to 4.88 since I tow everyday with it.

 

as posted above..

4:56 or dont bother...

its not unheard of to gain MPG cuz the entire truck is working less hard at a given speed with the steeper gears.

 

I have 4.10s in my truck, I tow about 7k trailer,and average 10 while towing 12-13mpg emptyhere in Alaska. I would reccomend 4.30 min or the 4.56 better.

 

What size tires do you have currently?

Think about gear changes this way:

Divide the new ratio by the old ratio. In this example, it's 4.30/3.73=1.1528

That .1528 is 15.28% INCREASE in torque to the ground at the rear wheels.

That's HUGE. It's the difference between slowing down going uphill, and speeding up. Or downshifting to keep speed, or being able to keep that speed without downshifting.

Now, on the flip side, that's also a 15% increase in engine RPM at any given speed and tranny gear. And it's also a 15% reduction in strain on the drivetrain to move the same weight.

Stop-and-go when empty, and towing, you WILL notice a big difference and probably get better MPGs while doing the same exact job.

Of course, how long it will take you to get used to it and start using the extra torque, well, that's up to you and your right foot

 

Thanks Art, That is the info I was looking for.

 

OK, so All of you are actually recommending this? @ what speed do you think the fuel/power ratio flips? I'm used to driving my old F-150's, so swapping from a 3.73 to a 4.30 or higher would have been great for gas mileage up until 50mph, when it would start going down hill, fast. I could see the swap if all he does is tow, but if he's gonna use it as a DD, then I can't see something bigger than 4.10 helping the gas mileage. Maybe I'm the only one who drives down the expressway going 75mph in my beast. I wouldn't mind trying the swap, but i just can't see the gas mileage improving. JMHO.

 

First, the original poster only asked about towing, so...

But ... the Ford modulars do not seem to respond as badly as previous generation motors to more gearing, and that includes the V10.

It's less strain on the drivetrain at all engine RPMs and all tranny gears, so stop-and-go will only get better (or at the very least stay the same) and highway will either stay the same or get marginally better, or might get marginally worse.

My '96 t-bird with a 4.6L came stock with 3.27 gears. Switching to 3.73s RAISED the highway mileage from about 24 to 26. And I wasn't doing 55 neither Mostly 75-80.

 

A little more info on my truck.

I only put on about 10K miles a year, and about half of that is towing my 5er. Another 1-2K of that is towing my Bobcat trailer. I probably only put on 3000 - 4000 miles a year while empty. I am happy if I get 12-14 mpg empty for that amount of use. I mainly want to see my towing mpg with the 5er increase.

When I tow now, I tend to have to run with OD off if there are anything but small hills, or it wants to shift. If it is windy I also need to run with OD off. I have not had the chance to tow the 5er on the freeway at 65mph + since the 5 star, without a 20+ mph wind.

Last year when I went to Yellowstone, I was able to run with OD on across North Dakota on the flats with no head wind at 65-68 mph, and I got 8.5 mpg. With overdrive off, I would get 7.5 mpg.

I assume the overdrive issue is from the engine only at 1950 rpm, and not in power band. With the 4.30 gears, I believe the rpm would be at 2200-2300 rpm. With OD off at 65mph, it is about 2600 rpm currently.

I also want more power for pulling passes. I tend to only be able to run about 30-35MPH on 10% or greater grades. Going up 14A last year it was 1st gear and 20-25 mph for 12 miles. It is 12-14% grades thought.


Oh, and stock 265/75/16 tires.

 

4.30's or even 4.56's ...

 

You want at least 4.56:1 and might even consider 4.88s.

 

Ok, now you guys have me thinking. What type of RPM would I turn at 65 mph in OD with 4.30, 4.56 & 4.88. I assume, sooner or later the RPM will get into that 2500+ range and my mileage will start to drop. I am ok with not being the fastest up the grades, but would like to get 9mpg on the flats. living in MN, it is farily flat, and going out west, I will go 400-500 miles on relatively flat land before I see any really big hills.

I am also looking at a DSL, but my truck only has 68000 miles and is paid for. I want a dsl, but it is hard to spend an extra 8-10K and get somthing that you really do not need.

I do not think that any DSL would avg much better than 13-14 mpg with the 5er.

 

...I guess that makes sense, my last F-150 was a 5spd w/ I6 300, before that was a few 5.8s. Anyone got a set of 4.30s for sale?

 

keep in mind these SD's are way heavier then a F150, so they respond better to regearing..

if you ask me the 3:73 should never have even been a factory gear combo..it suks..even with stock skinny tires. its just to dam much of a power robber.

 

You are correct on the rpm range in overdrive with the 4.30's. In direct it is about 3000 rpm at 65mph. My TT is about 9000lbs. Around here there are lots of rolling hills and it seems no matter which direction I go I have a headwind. I average about 7.5 towing at 62-63mph. It seems that in OD it will shift down just a little bit to soon. If I were to regear I would go with the 4.56 or 4.88 as has been recommended to you. The one time I did tow on a calm day I got 8.5, but that was only one time. A 5star tuner is on my wish list also. Hope this helps. John