Rear Axle Ratio Questions

DingoDog

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So ford stated the below 4 ratios are available

What axle gear ratios will be available?
A: Bronco 2-door and 4-door are available with: 3.73, 4.27, 4.46, 4.7

Please let me know if this is correct:
The 3.73 comes on non-locked automatic transmission Broncos.

The 4.27 comes in higher trimmed (BL, WT, and FE) Broncos with automatic transmissions.

The 4.46 comes on locked automatic transmission Broncos.

The 4.7 comes with manual transmission Broncos.

Am I right here? If not please correct me. Seems like all the 4.xx ratios would be best if I plan on not getting 35s initially but decide to get them later.





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SwankyTiger

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the BL with auto gets the 4.46
the 4.7 is on the manual BL and Sasquatch package
 
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Thank you for the chart I thought there was one out there but I couldn’t find it!
 
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DingoDog

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What’s with the outer banks and big bend having the two options for Auto Trans? What is it dependent on? Or can you choose when ordering
 

rtaylor

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Ok so what is the Outer Banks 3.73 vs 4.27 since it only comes in Auto? Oh wait.. is the 4.27 for the Advanced XFer Case?
My guess is that 4.27 is for 2.3L and 3.73 is for 2.7L. Optimized for street use instead of offroad.
 

KozMQZ

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This is helpful... qq... looking at 35"x13.50 or possibly 33x13" tires on badlands... which ratios would be ideal for those tires? Will 4.46 kill performance on 35's? Seems the 33's are fine with that stock ratio.
 

Designkid

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Ok so what is the Outer Banks 3.73 vs 4.27 since it only comes in Auto? Oh wait.. is the 4.27 for the Advanced XFer Case?
I'm thinking 3.73 is standard and the 4.27 is the optional locking diff available
 

Mountain Bronco

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I'm thinking 3.73 is standard and the 4.27 is the optional locking diff available
This is my thought as well. From my research the 4.27 is a sweet spot for 33s. This bumps my trim level up from the base model 3.73 unless I BaseSquatch.
 

kodiakisland

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As far as your question about what gears to get, always go low. With the overdrives on these transmissions, you almost can't get too low. If you plan on running 35s, go low.

If Ford is putting 4.70s on 35s at the factory, that tells me I'd probably be happier in the 4.88 to 5.13 range. I've never seen a factory vehicle geared too low. I see them geared too high for slow, off road use all the time, since they are going for average MPG for the EPA and not what actually works best.

Also, please don't compare gears from one completely different type of vehicle to another as some do because it's irrelevant.

I've regeared several vehicles. It's expensive and a pain, even if you do it your self. Save yourself some issues down the road if you are going to use this Bronco off road and go as low as you can from the beginning.

Another thing is the RPM range you want the gears to provide. Some motors need to be higher RPM than others, so you need to factor that in too. My Tacoma 4cyl is an absolute dog under 2,500 rpm and needs to be 3,000-3,500rpm for any serious work. It can not pull a hill in low rpms.

Many of the charts you look at for gears are based on a 1:1 final drive. You need a good calculator like this one to really see what you will be doing with your transmission and transfer case: http://www.grimmjeeper.com/gears.html
 
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edgeflyer

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Yep,
As far as your question about what gears to get, always go low. With the overdrives on these transmissions, you almost can't get too low. If you plan on running 35s, go low.

If Ford is putting 4.70s on 35s at the factory, that tells me I'd probably be happier in the 4.88 to 5.13 range. I've never seen a factory vehicle geared too low. I see them geared too high for slow, off road use all the time, since they are going for average MPG for the EPA and not what actually works best.

Also, please don't compare gears from one completely different type of vehicle to another as some do because it's irrelevant.

I've regeared several vehicles. It's expensive and a pain, even if you do it your self. Save yourself some issues down the road if you are going to use this Bronco off road and go as low as you can from the beginning.

Another thing is the RPM range you want the gears to provide. Some motors need to be higher RPM than others, so you need to factor that in too. My Tacoma 4cyl is an absolute dog under 2,500 rpm and needs to be 3,000-3,500rpm for any serious work. It can not pull a hill in low rpms.

Many of the charts you look at for gears are based on a 1:1 final drive. You need a good calculator like this one to really see what you will be doing with your transmission and transfer case: http://www.grimmjeeper.com/gears.html
Yep, all this talk about gear ratios is meaningless without knowing the ratios of the transmission. The 4.70 could be the equivalent of an old school 3.73 with 10 gears.
 

Rick Astley

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Real shame the BD Manual doesn't come with a 4.7. I wonder if it will be a dog with the 33"/34" tires it can almost certainly fit?
This worry has slowly been increasing as I view the BD as having 90% of what i'd ever need/want. However, the gearing and max crawl gear ratio, plus front locker (and 210) and 33" tires only being available in Badlands might see that $6K price bump become closer to necessary..... Which sucks as i've been pricing everything out based on BD and is in-budget. Buuuuuuuuuuuut, do it once, and do it right.

(Full disclosure: The only way i'm getting a bronco is with a manual transmission and I have less than 0 reservations about the 2.3 being more than capable for Bronco as it's in the gf's Ranger and I like the motor quite a bit)
 

Mountain Goat

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This worry has slowly been increasing as I view the BD as having 90% of what i'd ever need/want. However, the gearing and max crawl gear ratio, plus front locker (and 210) and 33" tires only being available in Badlands might see that $6K price bump become closer to necessary..... Which sucks as i've been pricing everything out based on BD and is in-budget. Buuuuuuuuuuuut, do it once, and do it right.

(Full disclosure: The only way i'm getting a bronco is with a manual transmission and I have less than 0 reservations about the 2.3 being more than capable for Bronco as it's in the gf's Ranger and I like the motor quite a bit)
I'm doing everything in my power to say just say "no" to Badlands. Back in the day, I had a lifted 1989 F150 regeared from 3.55 to 4.10 so it wouldn't be such a dog with 33s. Still always wished I had gone 4.56 or shorter, but it was enough to take the truck from being almost undriveable (no acceleration) to normal & manageable. That cost me $1,500 in Idaho dollars a decade ago, I imagine back East with my costal elites and high-dollar specialty shops, I'd be looking upwards of $1,000 per axle. And of course I'd be adding a front locker as well.

But yeah, that $6,000 jump does have the potential to kind of blow my budget out of the water. I'd like to make the BD work, even if that means running 32s for a few years. It just worries me that 32" seems to be at the top end of what Ford is willing to put on a 4.46 for this vehicle (base uses the same gears for 30s).

Oh, the days when 3.08 gears were enough to motivate my 3,100 lb Ranger! o_O

Now remember, if we stretch the gearing a bit, we'll just end up using "C" as first gear and have super long legs on the highway, so maybe this isn't the end of the world. Probably more important to get the 210mm front ring gear so we have the right hardware for future upgrades.

ETA: I think for now the solution is limit myself to running 33s (I had been eying 285/75R17 at 34" but the size is rare, and heavy), wait for the Ford Performance tune, and regear down the line if it ends up being a total dog like my F150 was.
 
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