I'm sure someone has tried changing gears to try to get better gas mileage so did it work? I have a 1975 F-250 4X4 460 automatic with 4.11 and 235 85R 16 tires which original came with 875R 16.5 and it only gets 8 mpg, yes I know it's a brick going down to road but these diff's are going to the scrap yard this week and there free, all I have to do is clean up everything and install them. Is it worth it ???? I will never haul or tow with it again. Its a toy.

Thanks
ARMSTRONGFORDTRUCKS

 

Are you just looking to get gas mileage out of it?

All in all it probably depends on how you drive. If you are 75% highway then the 3.54 will get better mileage with those tires but if you are stop and go 75% of the time 4.10 might be as good as its going to get.

Remember you have a 460 under the hood. Dont expect 15+ mpg by changing the gears alone. The engine/tranny condition and truck weight all play a part.


EDIT:
are these gears from like axles? 4.11 is a common 9" gear ratio and 3.54/4.10 is a common Dana 44/60 ratio.

 

OK I know I will never get great gas mileage, but 10 to 12 would be nice when I do take it on the road. It would be 4.10 with the Dana 44/60 ratio. My brother is junking this truck with the 3.54 gears and I have a chance to get them by hauling them away, just courious as to weather this would be worth the trouble, as I just put new ball joints, u-joints and paint on mine a x-mas time.

Thanks
ARMSTRONGFORDTRUCKS

 

How much do you want for the 4.10s? My dad and I both have newer f150s with the same engine and tranny options. The only difference is that his has 4.10 and mine is 3.55. Most of our driving is at about 45 on country roads. He gets about 1mpg better with the 4.10s. But I have noticed that above 55 I get about 2 or 3 mpg better than he does. It all depends on where and how you drive.

 

Years ago I did what you are asking when my truck was all stock. It gained overall 1 mpg driving in a 40 mile radius. It wasn't worth the trouble. It was like I lost 1st gear & gained some overdrive. The problem was I had to stick my foot in it twice as hard to get it moving so I didn't net much of anything.

 

I'm swapping the 4.11s out of my F-150 4x4 for the stock 3.50 ratio.

I had several F-250/350 powerstrokes some with 3.54s and 4.10s the 3.54s got 1 mpg better freeway, but didnt tow as well. if its a toy, being driven out of town, go 3.54s or 3.73s if you can find/trade for them. the 460/C-6 would like the 3.54s better.

my 73 F-250 2wd with a built 460 has 3.73s and gets 12-13 mpg (and roasts the tires at will...)

 

Sounds like I will be going to the 3.54 's to maybe get a little better on the gas, maybe just for something to do more than anything, besides the 4.10 's will be under the deck under cover if I want to swap back, it's just a saturday of work if I'm not happy. With that being said I will soon be getting my heads back to rebuild the 460, was going to get a RV cam for it, and a straight up chain and gears, maybe someone can suggest something better for the taller gears. I also will probably go to 33 12.50 16.5 tires in the future.

Thanks
ARMSTRONGFORDTRUCKS

 

Im with Mark

Unless you are driving a real substantial distance you likely will NEVER reap the rewards. Install kits for axles are $125+ alone and by the time you are done with it you will have at minimum $200. Think of how long it will take to benefit $400 at a gain of 9mpg over 8mpg with a 19gal tank.

 

I agree new u-bolts and center bolts are $80.00 but diff's are going to be removed anyhow for reconditioning and I have the parts here to put them back together, I have to say I'm still undecided on this as I only drove it 325 miles last summer, but I am very board, reall need something to do.

ARMSTRONGFORDTRUCKS

 

325 miles in 3 months is not worth your time or trouble. I would highly suggest getting the axles from your brother before he crushes them. Even the less desireable highboy D44/D60 combos will go for $3-400 on ebay.