Gear Ratio Swaps

[Winger57]

So waiting for my new Bronco as we’ve all experienced and fuel prices climbing we begin to think about the choices we’ve made. Now I wont be driving my Bronco every day but often enough that Ive wondered how to improve its fuel economy already. My daily commute is 110 miles and heavy traffic. So I try to ride my motorcycles when weather permits. First I ordered the BD because it does come with a somewhat narrower tire. But the gearing is 4:46 I wonder how much trouble it would be to go to 3:55s but mostly how that would work for the front differential… And in the long run would you be better off doing a gear vendors overdrive setup…. Anyone swap gears yet in these?

Sponsored

 

[dgorsett]

Very difficult, expensive and may gain you nothing. Broncos have very high overdrive gears anyway. My 2.3 auto with 4.27s gets 23 mpg over all kinds of driving.

 

[Nateandapril]

Gear ratio changes are neither easy nor cheap. There may (not sure cause I’m a Jeep guy that recently converted to Ford) be a ratio cutoff point where you have to go with a different carrier as well. In Jeeps the Dana 30/35/44 cutoff was 3.55. If you were 3.55 or numerically lower than you had to do an entire carrier swap to go to a numerically higher (4.10, 4.56, 4.88) ratio. So you’re talking a decent amount of cash. Parts alone would be 2-3k not counting the labor. Run the math at the difference in mileage which would be hypothetical and I think you’ll find it would take years to get back what you spent in regearing and you’d have a lower performance bronco the whole time

 

[mpeugeot]

So waiting for my new Bronco as we’ve all experienced and fuel prices climbing we begin to think about the choices we’ve made. Now I wont be driving my Bronco every day but often enough that Ive wondered how to improve its fuel economy already. My daily commute is 110 miles and heavy traffic. So I try to ride my motorcycles when weather permits. First I ordered the BD because it does come with a somewhat narrower tire. But the gearing is 4:46 I wonder how much trouble it would be to go to 3:55s but mostly how that would work for the front differential… And in the long run would you be better off doing a gear vendors overdrive setup…. Anyone swap gears yet in these?

Here is the ugly truth, it won't matter what gear ratios you run on the Bronco on the highway... period.

The 10 speed transmission overdrive is plenty for any reasonable highway speeds (up to and including 85 MPH). Changing gears will have a minimal impact on fuel economy.

On the surface, that does not seem to make a lot of sense. That's until you consider that the Bronco has the aerodynamics of a brick turned to have the greatest surface area into the wind. The number 1 factor in your fuel economy in the Bronco is aerodynamic load, which your speed (minus any tail wind) is the greatest factor. I can get nearly 25 MPG at 60 MPH, but barely 17 MPG at 80MPH.

 

[mpeugeot]

One quick addendum, tires can make a huge difference for commuting; (3+ MPG) just switching from my 33.5" M/T's to the stock OBX rims and tires.

I was testing this afternoon the difference between the two tires/rims. Over 21 MPG with the 32.1" and 17 MPG with the M/T's. The weight difference is pretty significant. Also, lowering the vehicle an inch doesn't hurt along with the more narrow 255 vs 295 tires.

 

[Snacktime]

I have a set a 3.73 I will swap you. I actually get better milage in sport mode at higher rpm. Big thing is going slow.

 

[kodiakisland]

In short, no, a gear swap isn't going to save you money.

 

[mjrcu]

I would probably just get a different car if you are trying to eek out more mileage by considering gear swaps

 

[edgeflyer]

My Bronco gets amazing mileage. Like 17.3 avg.

 

[jjack50]

A better choice would be a smaller high mileage tire than the 265-70 ATs on the Black Diamond. You could go with a narrower, harder, smaller, diameter tire (to reduce your ground clearance) or any combination of those changes in a road only tire if that's what's most important to you.

As for changing gears, It probably wouldn't be too difficult for the rear diff since it is designed for gear changes but the front diff would be another story since that open diff wasn't.

 

[Winger57]

Point taken. Not a aerodynamic machine. As for the tires. Well thats why I absolutely didn't want the Sasquatch package. I think I’d offend a lot of people lowering my new Bronco…. But Im sure someone will. And we all know the hybrid or full electric Raptor/Lightening Bronco is probably soon to be unveiled…. Dont think I will be ordering one of those either..

 

[BigDaddyRon]

i've had my wildtrack for a month now and found that at 65mph the rpms are 1500 or so. i have the 4.7 gears so they're pretty high. for example my 1967 chevelle had 3.73 with a 2sp powerglide tranny. at 65 i believe my rpms to be around 3k. with the 4.11 the rpms at 65 were like 4500. this is where the 10 speed transmission comes in. at freeway speeds the final drive ratio is so low that your turning around 1500 rpms. so really no need for the extra cost of swapping gears.

 

[Zeddead]

One quick addendum, tires can make a huge difference for commuting; (3+ MPG) just switching from my 33.5" M/T's to the stock OBX rims and tires.

I was testing this afternoon the difference between the two tires/rims. Over 21 MPG with the 32.1" and 17 MPG with the M/T's. The weight difference is pretty significant. Also, lowering the vehicle an inch doesn't hurt along with the more narrow 255 vs 295 tires.

I can attest that speed and the wheel size makes a huge difference to mileage as well. I commute ~140 miles, with the OBX as my only vehicle. I'm running MT 265/65's. I get 19mpg for the 70mph 1/2 of my commute and 23 for the 55mph 1/2. I'm averaging 20mpg overall for the last 2,800 miles.

 

[lapazleo]

Here is the ugly truth, it won't matter what gear ratios you run on the Bronco on the highway... period.

The 10 speed transmission overdrive is plenty for any reasonable highway speeds (up to and including 85 MPH). Changing gears will have a minimal impact on fuel economy.

On the surface, that does not seem to make a lot of sense. That's until you consider that the Bronco has the aerodynamics of a brick turned to have the greatest surface area into the wind. The number 1 factor in your fuel economy in the Bronco is aerodynamic load, which your speed (minus any tail wind) is the greatest factor. I can get nearly 25 MPG at 60 MPH, but barely 17 MPG at 80MPH.

Actually the number 1 factor in fuel economy in any vehicle is the driver, I say that as a 35+ year professional driver. But yes the auto in the Bronco has plenty of overdrive to maximize economy. I can also say the Bronco would do better in a wind tunnel test than you might think based on it's looks. Square lines don't always mean poor aerodynamics and round lines don't always mean good aerodynamics.

 

[lapazleo]

i've had my wildtrack for a month now and found that at 65mph the rpms are 1500 or so. i have the 4.7 gears so they're pretty high. for example my 1967 chevelle had 3.73 with a 2sp powerglide tranny. at 65 i believe my rpms to be around 3k. with the 4.11 the rpms at 65 were like 4500. this is where the 10 speed transmission comes in. at freeway speeds the final drive ratio is so low that your turning around 1500 rpms. so really no need for the extra cost of swapping gears.

4.70 gears are low not high. For example 3.73 gears are higher than 4.70 gears. All things being the same you can go faster with 3.73 gears than 4.70 gears. In gear ratios lower numbers are faster (higher) and Higher numbers are slower (lower).

Sponsored