Considering gear change

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I am thinking of swapping gears on my F250. We are going from a 4000lb dry weight, 21' camper to a 5500lb dry weight (6500 all up planning factor) Wild Wood 28'. I am currently running 3.73s (factory). I just ordered an addco rear sway bar, (truck had none), and am upgrading the shocks from factory Ranchos to Bilstein HDs. The truck has 71,000 miles on it. I am running 33" tires (3" taller than stock). Factory tow rating 9200lbs. I am considering 4.30 or 4.56s. The factory tow rating with 4.10s is 11,200lbs. I think the 3.73s will do it, but I live and camp in mountainous areas, plus the little V8 needs all the help it can get in general. Any thoughts on brand of gears, good diff shops in the central Tennessee area? 4.56 or 4.30? I don't think it will make much difference, but we have decided to keep the truck for a while, and in the mountains I think you need as much gear as you can get, and I am leaning towards the 4.56s. I had them in a 2wd F150, and they were great. I have the factory limited slip. Do I need a new carrier in a D60 and Ford 10.5"? WHAT I DO NOT WANT OR NEED IS ADVICE TO UPGRADE TO A V10, DIESEL, WHATEVER. Thanks for your time.
 
I'm sure you are already aware that you will need to put the same ratio in the front and the rear. If the truck is rated at 9200 and your towing 6500 I'd leave it alone.

The 5.4L triton, just isn't a powerhouse at towing IMO. It's the nature of the beast.
 
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Gearing change can really help with the big rubber. I always get my trucks with the shortest gears (higher numerically) that i can as the newer overdrive transmissions make them still very good cruisers on the highway.

If it was mine it would be 4.10's...
 
I'd pick the rpm you want in the right gear at the right speed and let one of the gear calculators pick the ratio. Off the top of my head 2500-2800 rpm in the 1 to 1 gear seems to be what's recommended for towing.
 
It seems that fellas that can 'properly' deal with setting up diffs are a small specialty group-a bit of a dying breed. I think the cost in parts/labor will be high. So, I might look at going the other diration with the tire diameter/height-at least as a test-good luck.
 
Seems to me that the cheapest option is to go back to 30" tires...

You decreased your gearing from a 3.73 to, roughly, 3.30 by increasing tire diameter by 3", or 10%...that's enough to make a noticeable difference...

But, if you need the 33" tires for ground clearance, then, yes, I would go with a set of 4.56 gears, that will get you to just below where you were...about the same as a set of 3.90 gears with factory tires...

And I would call the aftermarket folks. GM would require a new carrier once you go from a 3.XX to a 4.XX, but I don't know about Ford. Give Summit Racing a call, they'll be happy to sell you the ring and pinion set, as well as bearings, etc...and they'll know what you need to do the swap.
 
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Have you priced the cost of having gears set up and installed if you cant do it your self? My truck has 3.55 gears but the cost of swapping gears is more than the value of the truck so i just hang out in the slow lane. Maybe you should consider an underdrive box?
 
The 5.4 needs to be wound up to pull. I have pulled up to 5000 in a base model/ single cab F350 with 4.10 gears and it was definitely struggling unless it was wound up. The gas ZF-5 has a heck of a granny gear so getting it rolling was never a problem.

Stock size for the F250 was 235/85-16 right? Should be a 32'' tire - your tires aren't too much bigger than factory.

Not sure on the weight rating. Our F350 gas v8, 4.10, heavy service rear suspension is only rated to tow 9000 or something small; there are half tons today that can tow more than this truck.

With that said, it has absolutely no complaints about running at 3500-4000 to pull a hill and keep up with traffic.

If I was going to be pulling near the max weight, especially in the hills, I'd go for 4.30 or 4.56. When (hopefully) my parents sell me their truck - I am the only one that uses it - I may swap out to 4.30 or 4.56 depending on how much towing I am doing with it. One of the first thing I plan on doing when I get a house with a garage is learning to set gears. It's an art, but a useful one.

As for the carrier - the high pinion / reverse rotation Dana 60 does not have a carrier break. The Low pinion Dana 60 has a carrier break above 4.10 ... 4.10, 3.73 should use the same carrier. I know our F350 has a high pinion dana 60. Should be okay with the carrier. Depending on the integrity of the shop, you may be able to get buy with just a new ring and pinion. Most reputable shops that set gears will not let you get by with anything less than a full rebuild kit and a NEW ring and pinion.
 
Slap a supercharger on that modular, and run it about 8psi. That will wake it up and make it run like it should have when ford built it.
thumbsup2.gif


A little bit of boost can really turn a modular into something that runs well, an actually can tow without struggling.
 
Originally Posted By: Chris142
Have you priced the cost of having gears set up and installed if you cant do it your self? My truck has 3.55 gears but the cost of swapping gears is more than the value of the truck so i just hang out in the slow lane. Maybe you should consider an underdrive box?

My parents tow a slightly lighter trailer with a 2V 5.4 F150 and low ratio diffs. It spends a lot of time in 3rd at 2400-2800 rpm on the highway. They just drive it and don't worry about it, its got the trans cooler and the biggest problem is how much gas it uses. 90% of the time its just idling down the highway as a DD, so the extra mileage of low ratio diffs is worth some extra time in lower gears when towing.
Even with a 4.10, would your truck hold the TC locked in top gear going up any kind of incline anyways?
 
Originally Posted By: IndyIan

Even with a 4.10, would your truck hold the TC locked in top gear going up any kind of incline anyways?
Dunno. An OD was not available in my 1987 plus I refuse to own an automatic trans. But I find myself dropping to 3rd gear a lot even empty.
 
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I wouldn't bother its probably a 1000-1500$ job to change those.

Try driving it with the current setup first.. You might just have to drop down a gear on the hills.

If you go from 3.73 to 4.56 thats just about the equivalent of every gear being one lower?

so now you tow in drive instead of overdrive with 4.56?

For 1500$ I'd try the current setup first. 6500# is heavy but not absurd for the truck.

If it was 2wd with only the rear changing.. that's alot easier $$$ to swallow.
 
Originally Posted By: Astro14
Seems to me that the cheapest option is to go back to 30" tires...

You decreased your gearing from a 3.73 to, roughly, 3.30 by increasing tire diameter by 3", or 10%...that's enough to make a noticeable difference...

But, if you need the 33" tires for ground clearance, then, yes, I would go with a set of 4.56 gears, that will get you to just below where you were...about the same as a set of 3.90 gears with factory tires...



+1!

Rolling radius is just as important a part of gearing as the lay shaft..
 
I didn't realize 2005 came with 17s. The smallest size would have been 245/75-17 , 31.5''. Not too much of a difference between the two.
 
Originally Posted By: Olas
Originally Posted By: Astro14
Seems to me that the cheapest option is to go back to 30" tires...

You decreased your gearing from a 3.73 to, roughly, 3.30 by increasing tire diameter by 3", or 10%...that's enough to make a noticeable difference...

But, if you need the 33" tires for ground clearance, then, yes, I would go with a set of 4.56 gears, that will get you to just below where you were...about the same as a set of 3.90 gears with factory tires...



+1!

Rolling radius is just as important a part of gearing as the lay shaft..


+2! by putting on 10% taller tires, you have basically turned your 3.73 into a 3.39. It's a lot cheaper to back to the 30" tires. If you go to the expense of putting the 4.10 in with your 33" tires, you'd effectively be back at the 3.73, but with a lot less money in your wallet.
 
my only reservation about shorter gears is they can run a little hotter from what I've read for heavy equipment. Unlike the trans, the axle has no active cooling to protect it, so if you are towing heavy they say an axle temp monitor is better than a trans gauge.

My truck runs a 4.1 and it makes it a little easier to get going. But once I'm going, it's just a matter of what gear I select. With the 5 speed it stays locked out of 5th and usually pulls in 4th, and 3rd when trying to pass or climb. At level cruise it's somewhere around 2600-2800 rpm, as soon as it grabs third I'm between 4k down to 3k as it loads down.
 
Originally Posted By: Olas


Rolling radius is just as important a part of gearing as the lay shaft..


Except he wasn't talking about changing transmission gears.
 
Originally Posted By: Rand
Originally Posted By: Olas


Rolling radius is just as important a part of gearing as the lay shaft..


Except he wasn't talking about changing transmission gears.



That's right, he was talking about his rear diff.
Doesn't change the fact that tyre size has as much of an effect on your gearing as changing any other component after the splined output from the end of the crank, but before the driveshaft, does it?
 
Originally Posted By: Astro14
Seems to me that the cheapest option is to go back to 30" tires...

You decreased your gearing from a 3.73 to, roughly, 3.30 by increasing tire diameter by 3", or 10%...that's enough to make a noticeable difference...

But, if you need the 33" tires for ground clearance, then, yes, I would go with a set of 4.56 gears, that will get you to just below where you were...about the same as a set of 3.90 gears with factory tires...

And I would call the aftermarket folks. GM would require a new carrier once you go from a 3.XX to a 4.XX, but I don't know about Ford. Give Summit Racing a call, they'll be happy to sell you the ring and pinion set, as well as bearings, etc...and they'll know what you need to do the swap.


Smaller tires is definitely not cheap. I have BFG A/Ts with less than 10K miles on them. That set cost about $1200 (load range E). To buy a new set would be about another $1200, and would mean divesting myself of a set of very good tires....essentially costing about $2400 since I would be getting rid of a perfectly good $1200 set of tires. I might could recoup a few hundred for them on craigslist, but no, not the cheapest way to go. I think if no new carriers are needed, then we are talking about Maybe $700 in parts for bearings and gears, then the rest labor and a tuner, so maybe about $1750ish for the whole shooting match. As far as towing, I tow in "tow" mode with the torqueshift, so deeper gears would mean better response at low speeds, better engine braking, more time in 5th gear, etc. Plus, my experience with 4.56s in an F150 leads me to believe that deeper gears in a big truck with a little engine leads to better MPG as long as you cruise at reasonable speeds. I do about 65, 55-60 when towing. As far as heat in the diff, the 10.5 inch unit is pretty sturdy, requires 75-140 syn, and I have upgraded to the factory Ford finned aluminium diff cover, so that should take care of heat build up.
 
Originally Posted By: Miller88
I didn't realize 2005 came with 17s. The smallest size would have been 245/75-17 , 31.5''. Not too much of a difference between the two.

That was the size it came with. I thought it was more like 30.5, but if you say so, I believe you. I havent done the math since I bought the 33's.
 
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