Truck Gear Ratios

workingman · Jun 12, 2005

I am looking for gear ratio oppinions from members on Trucks that they use to pull there equipment. I currently have a 1986 Ford F-350 4x4 swr. with a 460 engine, auto tranny and 3.55 gears. Whats the best combo for brute force. Dreaming of a Diesel.
Thanks in advance.

Bird · Jun 12, 2005

Scotty, I'm not sure how to answer your question about gear ratios. The bigger the number for the differential gearing, the more power you'll have, but you need to have some idea of the weight you intend to pull, and also consider the gearing in the transmission. On an '86, I assume it has the 3-speed automatic. I had an '88 Chevy one-ton, single rear wheels, 350 engine, 3-speed auto, and 3.73 rear end that I used for awhile to pull a 10,000 pound fifth-wheel trailer. It wasn't bad, but it wasn't quite good enough to suit me either, so I traded up to an '89 Chevy Dually with the 454 engine, 4.10 rear end, and of course the 3-speed auto, but added a Gear Vendors overdrive unit. That was a real pleasure to drive. Then I had a '92 Bounder 40' motorhome, weighed in about 18,000 pounds, actually a '91 Ford 460 engine, 3-speed auto, and if I remember right, 5.11 rear end. I added a U.S. Gear overdrive unit to it and it was pretty good; not as good as a Gear Vendors, but not bad.

Each of the manufacturers publish a trailering guide showing their maximum "recommended" trailer weight, gross combined weights, etc. with different combinations of engine, transmission, and differential gear ratios. Any dealer should be able to tell you, or you can probably find the information on the Internet.

workingman · Jun 12, 2005

Bird,
Sorry, I do have a 3 speed auto with 3.55 gears. My tractor and trailer weigh 10000# and I would like more power. Just seems to not have enough UMPHH!!!! I figure that a 3.73 gear would be better but was just wondering what was the oppinion. I have pulled it with a 5.8L (351) F-250, 5 speed manual tranny and 4.11 gear without trailer brakes (short distance) It pulled really well with authority and the gearing also held back to aid with braking.

johnday · Jun 12, 2005

Scotty; Sounds like your a Ford guy too! That makes it easy to recommend to you. The 3.73 gear behind a PowerStroke makes for a REAL nice package. If I remember correctly, that's the only gear available with the stroker until you get into the dually. 4.10 or 4.11 are what most them are I think. I'm using an old '01 Stroker with 3.73 and I sure can't complain. It is turned up a little though, but even before that it was flawless. Maybe with a 4.10 in what you've got and an aux trans like Bird mentioned would work for you. But I think I'd be weighing the bucks you put into a 460 opposed to what you'd put into a truck already setup to pull like you want.
Let us know what you do, it's interesting to see/hear what guys do with their trucks. At least to me. /forums/images/graemlins/grin.gif

Av8r3400 · Jun 12, 2005

The question would be: How much towing, how much hauling and how much empty "daily driving" do you do with the truck? A gear swap is not a cheap thing to do (especially on a 4x4), so if it is something that you need to do, these questions are key. To have it done right (you'll need all new seals and bearings too), it will cost upward of $1500 to $2000 to re-gear a 4x4. Don't forget to re-calibrate the speedometer then too! /forums/images/graemlins/blush.gif

The higher the ratio (higher number: 4.10:1 or 4.56:1) the more low end pull you'll have, but sacrifice highway drivability and MPG's. The lower ratio (3.55:1 or 3.42:1) will give better empty, highway drivability but less low end grunt. Which is more important? Changing to 3.73's will help, but (in my opinion) will not make enough difference to justify the cost of the change. 4.10's would be better for the loads you are dealing with, but will make the truck a true gas hog.

Another possibility would be to take the money you will spend on the gear swap and put it toward a trade in on something set up the way you need.

RobertN · Jun 12, 2005

A big-block usually does not require real low gearing, especially when mated to an auto. They do not rev very high, and make good bottom end torque.

3.55's make a good all around gear for a combo like you have. You have plenty of torque from that big block to pull, but have gears that will give you better fuel mileage.

3.73's will give you a little more pulling power, and drop your mileage a little bit. It's a bit of a compromise gear ratio.

4.11's would be perfect for towing. But, your already terrible big-block fuel mileage will be REAL BAD... You'll jump 500-750 rpm at cruising speed.

For brute force with that gas engine, toss the auto for a 4-spd granny box. Switch the axles to 4.11's. The manual tranny will help a tiny bit with fuel mileage. If you put the granny tranny in granny 1st, you could pull about anything!

One thing of note that you did not mention, is tires. What tires do you have? Are they stock? If you put taller tires on that 4x4, you'll lose overall gearing. For instance, if your truck had 31" tall tires stock, and you switch to 33" tall tires, it has a net affect of changing your gears from 3.55:1 to 3.25:1. Taller tires are also heavier, and have a dynamic effect on the overall braking capablility of the truck.

If you are working or towing with your truck, stock or close to stock size tires are usually the best bet...

Gearing is not cheap. But, it does make a big difference in overall pulling "grunt". I swapped my old Ford F250 4x4 from 3.55 to 4.11. I had the 351 with a granny box. It made a big difference. But I took a hit on already poor mileage too... And, as someone else mentioned already, be prepared for a nice bill to go with it. You will not have to change the differential carrier for your truck(Dana-60 front, corporate rear), which is a +(unless you want posi's/lockers). Figure $750+ per axle minimum. IF you change carriers, figure $500+ per axle on top of the $750 for the labor and gears/bearing/seals. Those are ballpark figures based on the work I had done 5 years ago...