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I currently have 3.55 stock gears with 33x12.50 BFG All Terrains w/ stock 302 except for headers, 3in exhaust, and a fresh "Sixlitre Tuneup". The engine runs flawlessly and the timing is right on. I know that lifted trucks obviously get worse mpg than a stock one, however I am not doing too well in the past few months.

Within the past few months gas has gone up to $3.79 here in Houston, TX. I know its lower than some areas, but I really would like to do better so that I can afford to drive it on trips and not have to always hitch rides with other people.

If I were going to do a gear swap I was thinking 4.56's with a Detroit locker in the rear. I really dont do too much hardcore stuff but when Im out on the trails I wanna feel comfortable. There is a few guys on fullsizebronco.com that are running 4.56s on 35s getting around 15mpg.


I really would like to get some of the lower end power back and get my gas mileage back up as well. I was thinking that 4.56 would be a good upgrade and would give me alot of lower end grunt. Also, if I run 4.56 than I can always go with 35's and not feel bogged down. Many people have said that 4.10 really enough lower end for the 35's. What do yall think?

Most of my driving is under 50mph and alot of my freeway driving is in the 60-65mph area. I never really tach it much higher than that because its not comfortable and burns through the gas.

Give me yalls suggestions,

Thanks, Patrick

I have a 302 with a manual and 35" tires. I have not been able to get over 12mpg with 4.56 gears. It actually did better with the 3.50 gears on the highway.

My personal opinion is that 4.10 work great for 33's and 4.56 for 35's. Some like 4.88's 35's and you could get away with it with a 4 speed, but you would still turn more rpm's on the freeway.

i get 11 with 3:55 and 35's 9 in the dirt.
4:88 would be better for 35. 5:14's even.

5.8l with E4OD and I get 10mpg down hill with a tail wind... 35's and 4.88's but i love it in the dirt, where it belongs.

I've got 315 / 75 / R16 with 4.10's with an e40d trans and a 5.8 and get somewhere between 14-16 miles a gallon. At 2200 rpms at 70.

35s with 4.56 and e4od. 10mpg. 11 or 12 on a roadtrip not loaded down with cc set at 70 if im lucky

160k on motor

When I had the 3.55 gears I would get 400 miles from a tank of gas, since changing to 4.56 I get 300 miles on a tank..1996,351,e40d,33" tires...

BroncoDon wrote:When I had the 3.55 gears I would get 400 miles from a tank of gas, since changing to 4.56 I get 300 miles on a tank..1996,351,e40d,33" tires...

Ouch!

I'd be puttin' those 3.55's back in right about now..... the extra 100 miles per tankful would really save you some cash

BroncoDon wrote:When I had the 3.55 gears I would get 400 miles from a tank of gas, since changing to 4.56 I get 300 miles on a tank..1996,351,e40d,33" tires...

Same here....I call bs on you guys that claim anything over 11 mpg.

Man those figures are rough haha, For me now I think Im just going to keep the 3.55's in. Seems like I wouldnt be gaining much except for performance....which I wouldnt mind at all, but Im not ready to drop big bucks just for more grunt.

Thanks for the replies!

i really like the set up i have 3:55 with the c-6.lower rpms on the freeway and still enough lowend not to get stuck in 2wd.
swapping in the carbed 351x and bumping up the hp's also help me in my situation

When my bronco was stock, 3.55, m5r2, fresh 302, it got 15-16 mpg with a very worn set of goodyear 35" tires (read very light 33" tires). My huge fiberglass and front bumper don't allow that anymore.

I kinda wish I had kept the stock body and run 33" tires when I think back to that.

AusBroncodoc wrote:I'd be puttin' those 3.55's back in right about now..... the extra 100 miles per tankful would really save you some cash

It will save you some cash, right up until you melt the tranny... lol

I am on the same boat as all other 11-12mpg, 35s, e40d on 4.56s. I have a theory I follow, I put gas, and purposely ignore reseting the odometer, its never gonna make you warm and fuzzy, and if you can fill it up, then dont take it out.. lol

If I could get 16 mpg in a Bronco with a lifted suspension and large tires, I'd hardly ever drive anything else!

Now Ford just needs to come out with a Raptor style Bronco thats gets 16mpg. They should take the Raptor body and cut her down to a shorter wheelbase with 2 doors and maybe even have an extended cabe style that has a 1/2 door. That would be really cool in my opinion.

I pulled a pop up trailer and put 20 gallons of fuel in the bronco at pismo. That gave me just under a full tank. The f150 pulling an enclosed trailer got 28 gallons of fuel and the tank is 8 gallons more than my bronco. The f150 averaged 13.8 and when we got to wildomar, it had maybe 20 miles left. When I got back I had a quarter of a tank and made it to work and back. Mind you the f150 has a larger tank than the bronco.

tcm glx wrote:a theory I follow, I put gas, and purposely ignore reseting the odometer, its never gonna make you warm and fuzzy, and if you can fill it up, then dont take it out.. lol

I reset it solely to know how far I can go...sometimes the gas gage goes haywire eventhough ive dropped the tank 5 times to fix it.

hobbyturnedobsession wrote:I pulled a pop up trailer and put 20 gallons of fuel in the bronco at pismo. That gave me just under a full tank. The f150 pulling an enclosed trailer got 28 gallons of fuel and the tank is 8 gallons more than my bronco. The f150 averaged 13.8 and when we got to wildomar, it had maybe 20 miles left. When I got back I had a quarter of a tank and made it to work and back. Mind you the f150 has a larger tank than the bronco.

How do you calc mileage on "just under a full tank", "quarter tank" and "maybe 20 miles left"?

What F150 has a 41 gallon tank or why does your bronco not have the 33 gallon tank?