I have thought about this before. My 87 350 with 460 has a 410 gear ratio. Did you get all of that? I am thinking of changing the rear gear ratio to either a 373 or a 356 (?). The thought is, when I am going 55 mph the old engine is turning 3000 rpm's. It's got plenty of power and I am finding myself using the truck on more Highway and interstate miles. I am pulling a 20' gooseneck with around 14000 pounds. Would it be wise to change the gear ratio? Would I gain any fuel economy? It has a 4 speed manual tranny. 1st gear is like a granny and you can rap her out a 10 miles an hour. I figure that she would run around 2500 rpms at 60 with a 373, and it still has plenty of torque to pull hills loaded. Any comments will be appreciated.
FarmBoy350

 

it would be cheaper to install 33" tires to match your gearing

 

Ah so you would think.. I have a salvage yard near me that would sell me a rearend for $150. Now, you might say, well you just answered your own question...but, do you think that it makes sense to change the rear end out? It's a dually truck, and I'm not sure that they make 33' dually wheels.

 

If it's a 4x4, remember you have to change both axles. Figure on 500 an axle to do the job, and a negligible difference in fuel mileage. If you went to a 3.55, you might get an extra 1 mpg. The figure out how many miles you drive, and see if it's worth it.

14,000 is a lot of weight for a 3.55 axle. If it were me, I would just live with the 4.10 setup.

 

I agree with Andy. You're pulling alot of weight there and changing to a higher (numerically lower) axle ratio would be a step in the wrong direction. Your gas mileage while towing would likely go down with the 3.55's or 3.73's because the engine would have to work harder to pull the weight with less mechanical advantage (torque multiplication) at the axle gear. Engines use less fuel spinning higher rpms at part throttle than they do spinning less rpms with the throttle wide open.

For better mileage on the highway while unloaded, an overdrive gear in the transmission would be the best way to go about solving the problem. Either swapping to a trans with an overdrive gear, like an NV4500 or ZF 5-speed, or adding an auxilliary overdrive transmission in-line with the current transmission, like those made by Gear Vendors, US Gear and Ranger, are possible solutions. Check out www.gearvendors.com, www.usgear.com, and www.advanceadapters.com for more info on these aux transmissions. I warn you though, they are not cheap ($1500-$2500, plus driveshaft length mod).

I run 4.56 axle gears in my F350 with 33" tires, which gives me about a 4.30 effective axle ratio. I run this ratio with a C6 automatic, which has no overdrive gear. I'm very happy with the towing performance and my mileage (351 engine, 4x4 truck) is pretty good even with this low axle ratio, as long as I keep the speed down on the highway. I do hope to someday put in a Gear Vendors overdrive unit so I can cruise at interstate freeway speeds and still get good mileage. Untill then, I stick to the right lane on the freeway or drive the 2-lane highways instead and enjoy the ride .

My old Chevy dually had a 454, TH400 (no overdrive), 4.10 gears and stock tires. It drank alot of gas when I used it as a daily driver, but I would not have wanted anything less than 4.10's in it when it came time to get some work done . I just took it easy and drove a little slower on the freeway.

 

I'm pulling a 3 horse slant Featherlite now. Used to pull a steel frame 26' w/living quarters hauling 3-4 horses and gear. With 3.55 gears I get 10 mpg average on the interstate/flat roads. Once in the foothills going to a jackpot I got 6-10 mpg with the 3.55's. With the Featherlite I'm getting 8-10 mpg with 3 horses and my overall mileage is 10-12 mpg. There is a lot of traffic in the Atlanta Metro area and this eats gas. I never pull in overdrive and could with an overdrive box inserted. As I haul only on weekends to jackpots mostly now, I am content with the performance. I'd stay with the 4.10's if I were you with a 14,000 load. I am at 7,400 with the Featherlite and probably could pull OD on the interstate, I just don't with the E4OD, why mess with it? I am very happy with the truck and will keep on going as long as I am able. The reduction in load was the greatest contributor to mileage. The 460 has the power to pull a grade with your load easily, especially with the 4.10's.
Tex

 

I have heard people talk about the life or death of a pulling engine. RPM's are everything. The truck is an 87. It's got 18 years of pulling under her belt, and now that I have heard your arguments for not changing my rear-end, maybe I will reconsider my idea. By changing something, I will probably end up having to change out my engine as well. It's got 95k miles on her, which I think is low. Thanks for all you inputs. Maybe I will just retire her and use my powerstroke. thanks,
Farmboy350