I have an '04 Ford F-250 XLT Super Duty with a 5.4L & a 3.73 rear end. My question is, would it be worth it to change out the rear end gears to a 4.10 to gain gas mileage? I do pull a travel trailer weighing in at 7200#s.
If you are going to continue to pull that weight, I would leave it as is.
gearing down the final drive would decrease your mileage. Even if it did provide a mileage benefit, the money you spend to have it done would probably be more than you save on gas
The 4.10 gears will be much better for towing and will improve fuel economy while towing.
You might take a small hit in mileage when not towing, but nothing to wory about.
I regeared my k5 Blazer to 10% lower (numerically higher) than stock and fuel economy did not change.
Yup, your thinking is reversed. You would need to go to a 3.55 or 3.27 to get better duel economy. Changing just ?one step? is viewed by most to be not worth the trouble/expense by most people. I agree that you should keep what you have if that is required by the tow rating for your vehicle. There used to be aftermarket differentials or auxiliary transmission that had high and low ranges. If they are available, they are probably a big investment.
It’s a lot easier and cheaper to find a complete rear end, brakes and all, and change the whole thing. But you can’t have your cake and eat it too, unless you go to the expense of a 2-speed auxiliary transmission. A 4.10 will tow heavy loads better, but a 3.25 will give better mileage…It’s not worth the effort, really…
Joseph_E_Meehan is correct, as usual. Don’t mess with it. Spinning the engine faster will gain you next to nothing except faster pick up in your pickup. You might get better towing mileage, but only if you were content to drive 10 MPH slower.
You think it gets bad mileage now? Go to a 4:10 gear.
The Ford can tow without messing around with it. The Chevy guys used to talk about their headers and RV camshafts, their Aluminum intakes and great big aftermarket carbs. You ask the Ford guys if they modified their rigs and they would say no. Just no.
Thanks for all your replies, not sure what I am going to do yet but I dont think I will be changing gears because ford wants $1300.00 to do it and they say I may see a 4 mph gain. I may just trade it in on something that will pull my 7k# camper. I have been looking at the Nissan Titan crew cab that they say can haul 9900# with a factory installed towing package but they are pricey.
hmmm, forgot to sign in for the above post…
This is not true.
Going from 3.73 to 3.55 gears will lower RPM but will also increase engine load. The result will likely be decreased fuel economy, especially while towing, due to higher engine load. To better understand this relationship look at some EFI fuel maps, and look at how quickly injector pulse width increases with engine load.
Will that use less fuel than the Ford?
from what I have learned it(Nissan Titan) will get about 15-18 mpg city and about 10 mpg pulling the trailer. I am waiting on a friend that just bought one to confirm this as he also has a trailer that weighs 7600#s. My F-250 now gets about 12 mpg city.