Axle ratio

Hi, I have a 2003 Ford F-250 Crew cab 4x4 with a 5.4L and a 3.73 axle ratio.  With this combination, my tow rating is only 6800 lbs.  Ford lists that with no other changes other than switching to a 4.10 axle ratio, my tow rating increases to 8400 lbs.  I talked to my local transmission shop, and they said they can change it to a 4.10 easily enough, but they felt I would be happier with a 4.30 axle ratio after I told them why I wanted to change it.

I'm looking to buy the Rockwood 8317SS which weighs in at just under 6000 lbs empty and has an 8273 GVWR.  I'm new to this game, but have done some reading.  I was a little disappointed when I realized a truck as large as mine could only tow 6800lbs, but I guess with only a 5.4, it's a lot of weight to carry let alone a trailer too.  I also realize the gas trade off with switching to the higher ratio, but I only work 2 miles from my house and I don't do any interstate driving with this vehicle other than when I will be hauling the trailer.  That's why there's only 50,000 miles on the truck.

Has anyone else made an axle ratio change?  Any success stories, horror stories, etc....  I guess the transmission shop calls this a (Ring and Pinion) change.

Thanks in advance,

Tom

Welcome to the Forum.
Your limiting factor is and always will be the motor, not the rear end ratio.  While a gear change will help. nothing will cure the screaming you will encounter at times.  If you want to know what a 4.30 rear end ratio will sound like when towing, stick your transmission in 3rd and get the truck up to 65MPH.  I suspect you will not enjoy the screaming motor.  Why not find a similar truck that already has a V10 in it and word a swap?  You would be much happier towing at the end of the day IMHO.

Hi explorer and welcome to RV Forum...

I think the 4.10 will do the job. A 4.30, while giving even better towing performance, seems like overkill and it will definitely drive the engine RPMS up even further, as Donn describes.  Your speedometer and odometer will have to be recalibrated for either axle ratio.

Thanks for the input guys, always appreciate another set of eyes.  When I was researching this I came across this chart which shows optional rear ends that Ford puts into their F-250's:  ( I have the "C1" currently listed below )

The following lists the gear ratios on rear axles.

31 ? 3.73 non-limited slip, F-250/Excursion
C1 ? 3.73 limited slip, F-250/Excursion
32 ? 4.10 non-limited slip, F-250
C2 ? 4.10 limited slip, F-250/Excursion
33 ? 4.30 non-limited slip, F-250
C3 ? 4.30 limited slip, F-250/Excursion
36 ? 4.56 non-limited slip, F-250
C6 ? 4.56 limited slip, F-250

I also came across this:  http://www.trucktestdigest.com/axle%20ratios.htm

I'm going to go back and research this more before I do anything.

Thanks,

Tom

PS - I should have also mentioned that I live up near Pittsburgh Pennsylvania where there are nothing but hills and mountains.

  Seems kind of an expensive change considering you have to change the front too.

Yea, I got a quote and the cost is around $1,900 labor and parts.  But when I consider the alternatives:

1.) Buy a new truck, about 35K to start, on top of a new camper at about 25K, I'm looking at 60K before taxes.  I can't get Congress to bite on that much pork barrel spending.  I'm still fighting with her on buying a camper. 
2.) Buy a smaller camper, (We really like the floor plan of the 8317SS for our family of 5)
3.) Buy a used truck.  ( I hate to do this since I bought mine new, kept really good care of it, and it only has 50,000 miles on it.)

So the $1,900 started to look like my best option. 

If I go with the 4.10, it bumps me from a tow rating of 6800 to 8400lbs
If I go with the 4.30 that the shop is recommending, it would bump me from 6800 to 9200lbs. 

But that is why I asked the question here,  I wanted to get some other opinions and also see if anyone else has gone this route and how they liked it.

Check out this article though, it is pretty good:  http://www.trucktestdigest.com/axle%20ratios.htm

Thanks,

Tom

Hi, I live in a hilly and mountainous region of Pennsylvania near Pittsburgh.  I have a 2003 Ford F-250 Crew cab 4x4 with a 5.4L and a 3.73 axle ratio.  With this combination, my tow rating is only 6800 lbs.  Ford lists that with no other changes other than switching to a 4.10 axle ratio, my tow rating increases to 8400 lbs.  I talked to my local transmission shop, and they said they can change it to a 4.10 easily enough, but they felt for the same money,($1,900 parts and labor) I would be happier with a 4.30 axle ratio after I told them why I wanted to change it.  The 4.30 gives me a 9200 lbs. tow rating.

I'm looking to buy the Rockwood 8317SS which weighs in at just under 6000 lbs empty and has an 8273 GVWR.  I'm new to this game, but have done some reading.  I was a little disappointed when I realized a truck as large as mine could only tow 6800lbs, but I guess with only a 5.4, it's a lot of weight to carry let alone a trailer too.  I also realize there is a trade off with switching to the higher ratio, but I only work 2 miles from my house and I don't do any interstate driving with this vehicle other than when I will be hauling the trailer.  That's why there's only 50,000 miles on the truck.

Has anyone else made an axle ratio change?  Any success stories, horror stories, etc....  I guess the transmission shop calls this a (Ring and Pinion) change.

The following lists the gear ratios on Ford F-250 rear axles. ( I have the C1 listed below, but looking at either the C2 or C3 ).

31 ? 3.73 non-limited slip, F-250/Excursion
C1 ? 3.73 limited slip, F-250/Excursion
32 ? 4.10 non-limited slip, F-250
C2 ? 4.10 limited slip, F-250/Excursion
33 ? 4.30 non-limited slip, F-250
C3 ? 4.30 limited slip, F-250/Excursion
36 ? 4.56 non-limited slip, F-250
C6 ? 4.56 limited slip, F-250

I also came across a pretty good article on this worth reading:  http://www.trucktestdigest.com/axle%20ratios.htm

My alternatives are:

1.) Buy a new truck, about 35K to start, on top of a new camper at about 25K, I'm looking at 60K before taxes.  I can't get Congress to bite on that much pork barrel spending.  I'm still fighting with her on buying a camper. 
2.) Buy a smaller camper, (We really like the floor plan of the 8317SS for our family of 5)
3.) Trade for another used truck.  ( I hate to do this since I bought mine new, kept really good care of it, and it only has 50,000 miles on it.)

So the $1,900 is starting to look like my best option. 

I'd love to hear from someone that has already done this.

Thanks in advance, I posted to another group and realized this one was probably where I should have posted this.

Tom

Like I mentioned before, before you spend a dime on any changes take the truck out on the interstate in third gear and see if you can stand it for hours on end.  Then make up your mind.

I'd go with the 4.1 and then look at a GearVendors overdrive  (see:http://www.gearvendors.com/) . I have one in my Dodge Ram diesel 3500 and love it. I have a 4.10 rear and my son-in-law has a 2500 diesel Ram with a 4.10 rear. He does not have the GV overdrive. I can get 22.4 mpg on the highway with my truck and the best he can do without the GV is 16.5 mpg.

The 4.30 ratio is a popular option to consider if you've got some 'hilly' travels... especially with the 5.4 L engine...IMHO

We have an F-350 (4x4 5.4L) with a heavy Lance Camper...I got the truck, used, before we got the camper, and it had 3.73 gears...

Out here in the West, I wanted more pulling power with the camper aboard...I looked at changing to the 4.30 ratio first, but then decided to go to 4.56 gears as I wanted some low ratios in 4x4 LOW for some use on sandy beaches and some rough off-road running...otherwise, the 4.30 seemed to be ideal....

I had West Coast Diff's in Sacramento, CA  do the changes - 4.56 gears (two diffs), new bearings, two new rear axle shafts, and a Detroit Trutrac LS in the rear diff - About $2200, two years ago...not bad for a 4x4! and in one day to boot!  Those guys were great!

I haven't noticed hardly any difference in fuel mileage when loaded with the camper before or after the ratio change, about 9.5MPG...I don't use the truck for other stuff, so unloaded MPG isn't an issue for me...

I don't think an 'overdrive' add-on transmission is such a good 'deal' unless you run lots and lots of highway miles - you'll need lots of 'miles' to get any real pay-back in fuel savings to pay for the unit...IMHO

I haven't seen the need to change the 3.73 gears in our Excursion yet, as the V-10 engine makes a big difference in the 'power' department...and we still are getting about 9.5 MPG in it's current mode...

Ray

Explorer777,

I've merged your two topics that way you can follow the messages more easily.

Marsha~

Thanks MEXRAY, I was looking for someone like you that had already gone through this.  What do you think about Donn's comment above?  Is it an annoying trade off going down the highway since you changed over? Also, did you have to have your on-board computer re-flashed so the the speed odemeter, etc. was working properly?  Did you notice the the improved pulling power, was it worth it?

Thanks in advance,

Regards,

Tom

If I were you I would go for the 4.30's, with that ratio on the flats you should easily be able to hold OD and in the hills it will pull very nicely.  One thing to consider is that when you in the hills and mountains you aren't going to running 65 mph, more than likely you will be down to 55 mph or maybe even in the 40-45 range if it is a steep grade, so your RPMS won't be as high as below when running lower speeds but the 5.4L will be in its power band.

Here is a little brake down of roughly what your RPMS would be at 65 mph:

Gear Ratio      RPM with OD off (1:1 ratio)            RPM with OD on (.71:1 ratio which is OD for the 4R100 and E40D)
3.73                    2550                                                    1820
4.10                    2800                                                    1990
4.30                    2920                                                    2075

PHS79, great information!  Here in southwestern Pennsylvania, you are lucky to get up to 55, let alone 65 with all the hills and turns.  There's a couple of pulls coming out of Meadville right off the interstate where you are pulling out of a sharp cloverleaf right into a steep 1 mile climb.  A co-worker of mine that already has a camper warned me about this which is what started me down this discussion to begin with.

Regards,

Tom

Tom, I don't think you'll even notice the difference in running down the road with a 4.30 vs the 3.73's...look at that RPM chart above - there's not that much difference at normal 'towing' speeds...

I hardly notice the difference in our F-350 with the 4.56 gears, but I travel with the camper at only 55-60 most of time - not a speed demon with the big 'sail' sticking up there in the air with our 4 in suspension lift and 34 inch tall tires!

I didn't go the to trouble to changing the computer to correct the speed - the shifts seem to be in order as they are...I check my speed with the GPS to keep close the the speed I need...

Ray

Thanks Ray, I think I'm going to go ahead and make the appointment.

Best Regards,

Tom

Their is no dough that 411 are better pulling gears but how much are you actually going to pull the camper? I have pull a bumper pull in 3rd behind a 454 gas and it pulled just fine ate a bit more fuel but pulling a camper what do you except. slow down enjoy the view life is short you might see something that like along the way. The reason I pulled in 3rd was to save the overdrive from shifting up and down too much the 454 has the ponies but i did not want to spend money on the trans if i did not have too. ;D 8)

Hey Explorer..I had the same truck you did, except mine was only 2X, not 4X4.  I went from the 3.73 to 4.30 (changed the whole rear-end, since someone was selling it!).  Nothing needed reprogrammed (no computer stuff).  The RPM's listed above were just about dead on (good job whoever found those!).  My gas mileage changed very little to none.  Unloaded I still got between 15 - 16 mpg.  Loaded with my 5500lb travel trailer, I would get anywhere from 8 to 11 mpg.  As was noted above also, "cruising" speed with the TT didn't change a lot.  Where you will notice the difference is in the "get up and go".  From a dead stop, you will be able to get to cruising speed much easier.  This should also help in those mountains, though you won't be doing it at 55 or 60 mph!  Again, depends on the actual mountains.

Now as far as the tow ratings, I also was going through the same things you were.  For this year model (2003), the only optional gears available were the 4.10.  So legally, the tow rating you listed of 8400 pounds is the highest you can go to.  Technically, you would be correct in your tow rating of 9200 pounds, however, since that was not a factory option, it legally does not exist.  What it will do for you is give you a "comfort factor" for towing.  However, you would still be bound by the 4.10 rating of 8400 pounds.

Now, we'll talk realistically.  Even with the above mods made, and with the trailer you are looking at, you will be at the very limit of what your truck can do.  Yes, the 5.4L will scream.  The 6.8L will too, it just won't mind it as much.  I towed my TT everywhere with OD locked out, sitting right at about 2900 RPM, and the 5.4L will do that all day.  You will have some "issues" with the hills, if they are what you are describing, however, you will be fine.  Let the motor do it's job.  It will.  Just don't be in any hurry to get anywhere.  I put 125,000 miles on my old 5.4L, and the guy I just sold it to has a camper very similar in weight to what you are thinking about.  I have no reason to doubt that he won't get another 125,000 miles from it.  It's a good truck, it's just not a powerhouse diesel.  But you have to think realistically.  Do that and you'll be fine.

The received wisdom is that a gear ratio change doesn't affect real-world mileage much if at all.

Changing gear ratios will increase the life of the transmission and maybe the transfer case.  It won't do anything else.  You will have to decide whether it's worth it.

Me, I'd tow with the truck the way it is for a while, and then decide whether to stay with it and whether to do the gear change.

The towing rating and GCWR are not legally binding limits.