Ok I will try to explain this the best I can. I was talking with a guy last night about my truck and telling him that I may want to put 4:30 gears in it if I dont like the way the 3:73s pull my camper. He asked why I would do that so I tried to explain that the modular engines like the higher revs and it was to my understanding that they pull better at high revs. His responce is put it in drive then. You would get the higher RPMS thus saving on the cost of the gears.

So this is were i get confused. What he said makes sense to me. Why would you put the 430's in the truck? If it is so you can pull in O/D to save gas milage? If that was the case wouldnt you get basically the same milage with the 373s in drive? Or is it because it is easyer on the tranny?

I really hope some one can make this clear for me because right at the moment I is reallly confused!!!!!

Thx Guys
Oh I drive a 99 f250 SD 4x4 V/10. Just incase i get a responce saying "what do you drive"

 

You're "confused" just because there is no one answer. You are ultimately asking "what combination of power and gas mileage suits me", and only you know that. There's absolutely nothing wrong with running in a lower gear to tow a load, as long as you don't mind the reduced speed. For instance, if the truck is normally used as a daily driver, and you only occasionally actually tow a load you might legitimately prefer the 373's because you'll get better mileage 95% of the time.
If you change the gears you'll have noticibly more power, but 95% of the time you won't need it!

Mostly you just need to drive with your camper and then decide. If the performance suits you, what's the problem? By the way, the 373's in my observation seem to be associated with many of the posters who claim insanely good gas mileage, like maybe 15 mpg. The problem of course, is that the power is addictive. If you do change gears you'll never go back...!

 

BareBones did a good job of explaining it. 4.30 gearing will give you better towing power in either direct or OD but with a trade off in fuel economy.

Welcome to FTE and thanks for joining us in the Towing forum!

 

What about puting in 4.10's instead.

 

As far as for the 4.30 for pulling if you ever have them you will never want anything else. As far as mileage goes it depends on how you us your truck when not pulling. My DRW is the only truck that gets close to being empty will do fine on the highway up to about 65 mph (13 mpg) if I go over that it will drop to 11.5 to 12. But I rarely run it empty so for me its no problem plus I have 215/85/16 tires which also makes a big difference with both power and mileage.

As far as the tranny goes the lower gears will put a lot less torque on it and it will last a lot longer with the lower gear.

And the 4.10 gears may be worth looking at it really depends on what you do with your truck when not pulling. When I bought my first 2000 F350 SRW I wanted 4.10 but in the F350 all they offered was the 3.73 and the 4.30. So I went with the 4.30 and have never looked back. But both of my trucks get worked hard with heavy loads and not much empty running.

Denny

 

What About 3.55 With 17" Tires.. Is That Good? Is It Not True Lower The Number The Less Times Drive Shaft Moves? Can You Pull 8,000# With This Comb I Have 5.4 Screw 3.55 255/70/17... I Hope It Pulls Ok..

 

MERENE, your setup is fine depending on what your towing, how far your towing it, how often, and at what elevation, clear as mud right! The 5.4 is best mated to 4.10 gears for towing anything relativly heavy. For example I tow my boat and camper together about 5-10 times per year. My total combined wieght is a hair under 17k lbs. I am only driving maybe 50-100 miles each way, and being in ND Elev doesn't come into play, the only obstical I have are the rolling hills. I have 3.73s mated to my V10, for my situation they do an adaquate job, no I can't tow it in OD but for the 2000 miles a year I might tow this I'll sacrifice and tow it in drive. I probably tow a combined 3000-4000 miles per year but the rest of those miles tally up less than 5k lb trailors for the most part. Now the 4.30s would be nice but I wouldn't be gaining much for my situation, the 3.73s have yet to slow me down, or not allowed me to tow anygrade at 65-70mph, and I have always made my 8mpg doing so! If I were towing this combo 10k miles per year I'd have the 4.30s, If I were to buy a larger camper and my weight were to go up to 19 or 20k lbs I'd have the 4.30s and lastly if I towed in any of the mountains I would probably have 4.56s! I don't know if I explained to very clearly but when it comes down to it, it all depneds on these factors and what compromises your willing to make and what your definition of adaquate towing is.

To the original poster as I just said it really depends. the 4.30s are great..............depending on what your towing, how often your towing, at what elev your towing ect ect ect. The one thing holding me back is I live on the prarie where the hwys are wide open, speed limites are realitivly high and when I run unloaded I am usualy running all of 75mph and sometimes 80mph, w/ 4.30s at that speed I would most definitly lose some mpg, then again what I loose emty I would probably make up when towing.

Also to the first question, The reason for 4.30s is they will essentialy put you right in the sweet spot in 3rd (D). with the 4R100 at 65-70 I run 1800-2000 rpms in OD, in third I'm at 2700-2900rpms. keep in mind the peak torque on the V10 is at 3250rpms. with 4.30s your basically running 400rpms higher than 3.73s. this would put me at 3100-3300 rpms in 3rd (D) which is better suited for towing heavier loads or pulling steeper grades without dropping to 2nd. I have one hill that I cann't quite make in 3rd unless I lose about 5-7mph, now when I drop it to 2nd I can accelerate going up this same hill. If I were to have the 4.30s I would more than likely be able to hold my speed without dropping to another gear.

 

How much weight are you pulling. When I am all loaded up with my toy hauler I am about 20,000 - 21,000 lbs total. I have pulled this in drive with the 3.73 but the truck didn't like it much. I changed to the 4.30 and still tow in drive, only now it tows the weight better, especialy on the steep hills. I used drive either way because OD is too steep a gear for the weight I am pulling.

 

You sure got a bunch of good answers here on a VERY confusing subject and for the most part I can't improve on what has been said about your situation. Looking through a Ford Trailer Towing Guide for 1999 the ratio change will add 3,000# to your gross combined weight rating (GCWR) but as far as Ford is concerned your maximum trailer weight in conventional towing is 10,000 either way and for a fifth wheel application comparing 3.73/4.10; F250 4X4 regular cab 11,100/14,100, extended cab 10,800/13,800 and with a crew cab 10,500/13,500.

I recently upgraded to a new(er) camper that's a couple feet longer, a little higher, slightly wider and ~2,500# heavier. The old 3.55 ratio worked well for the bulk of our towing with the old trailer except it wasn't overly fond of our bi-annual southern Colorado trips. It just doesn't quite make it with the newer rig and we're looking at a new set of 4.10s to make it work the way it should. I've even had people suggest I may see a mileage increase when I'm towing and that's 95% of Clyde's job.
__________________
Roger

Clyde S Dale, my chestnut brown & tan 5th wheel workhorse is a
1984 F250HD XLT RCLB 4X2 8600 GVW
460 C6 3.55's
68,500 original miles (and counting)

 

Hi Guys: Just to add more confusion to this topic, it seems that no one is talking about final drive ratios. A 4.30 rear axle with the 4r100 transmission in overdrive with a will have a final drive ratio of 3.05. A 3.73 rear axle ratio in drive will have a 3.73 final drive ratio, in drive and a 2.64 ratio in OD. The transmission should run cooler because its running in direct drive. I realise that the truck with a 4.30 rear axle has 4 gears as opposed to 3 with the 3.73. the 3.73 final drive ratio should out pull the 3.05 and shift less. When the 4.30 downshifts it will then gain the power advantage.
After saying all this, unless I was towing most of the time, I would stay with the 3.73 rear axle ratio.