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Old 10-31-2013, 09:16 AM   #1
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3.21 Rear End mileage vs. more torque

getting ready to order (Unlimited, 6-speed, round-towner, no rock climbing). Can I assume that if I go off-road (mud, water, some inclines, etc.), but not severe inclines or rock climbing, that the 3.21 will do fine? Also, how much real variance might one expect for the 3.21 with 6-speed manual vs. the 4.21 with automatic?

thanks for any info

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Old 10-31-2013, 09:19 AM   #2
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getting ready to order (Unlimited, 6-speed, round-towner, no rock climbing). Can I assume that if I go off-road (mud, water, some inclines, etc.), but not severe inclines or rock climbing, that the 3.21 will do fine? Also, how much real variance might one expect for the 3.21 with 6-speed manual vs. the 4.21 with automatic?

thanks for any info
If you are ordering, get the highest numerical value. The MPG tradeoff (maybe 1 depending on how you drive) isn't worth it. 3.21s IMHO are too low for a V6. I owned a 3.21 Sahara for 2 years and just traded it for a 4.10 Rubi. If you plan on modifying your rig at all get the higher gears.

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Old 10-31-2013, 09:20 AM   #3
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I don't think the gearing really becomes a big deal until bigger tires are used. My buddy has a JKU with 6 speed, 3.21's and 285 sized Duratracs and it does fine.

You could always opt for the 3.73 rear gears with the Sport.
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Old 10-31-2013, 09:37 AM   #4
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If you aren't going to off-road or tow much I'd recommend the 3.73's. I would steer clear of the 3.21's since you will likely get bigger tires at some point and it'll feel under powered.
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Old 10-31-2013, 09:42 AM   #5
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I have 3.21's and P255/75/r17 GY SilentArmor and it does "ok". Sometimes in wind it struggles, so I keep it in 5th. 6th gear really becomes a "highway only" gear at that point. My brother has 3.73's and there's a noticeable difference compared to mine.
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Old 10-31-2013, 09:49 AM   #6
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A bit different perspective. In general, if you are going to keep about the same tire size, IMHO the 3.21 with a manual will be fine. Off road you will be fine since you have the tcase in low/hi or 12 speeds to work with. Tons of options. With a manual you get to choose the shift points, no so much with the auto (you can stick it, but it's not the same). You'll probably get a bit better mileage with the 3.21's

Where the 3.21's don't shine is with larger/heavier tires with an automatic - especially if you are at elevation (ie Denver area and spend time on 70)

Unfortunately Jeep raised their prices up to 10x (from early '12 models to present) on gear changes - so look at that on the window stickers.
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Old 10-31-2013, 09:59 AM   #7
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thanks all. A real mixed bag of opinion, but that's OK. I think I'll be sticking with the 3.21, since I don't see ever doing a lift kit or much bigger tires. Thanks
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Old 10-31-2013, 10:08 AM   #8
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Test drive each before making your decision. You will see a ton of difference between the 3.21 and the 4.10. I run 4.10 on 33's. I've sacrificed a little gas mileage (17.5 blended city and hwy) and I tend to be a pretty heavy throttle guy with me 6 spd.

3.73 is great for DD with 32's/33's. But so much is personal preference, that is why testing each would be so helpful.
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Old 10-31-2013, 10:20 AM   #9
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Since you're ordering a 6-speed, I'd also opt for the 3.73s. It will feel a tad more peppy.

My '12 had 3.21s and a 6-speed, and my '13 has the 3.21s with an auto. Huge difference in usable snort with the '13, the auto hauls the mail pretty well with the taller gear. My '12 was a gutless turd in comparison. Not sure if the gear ratios in the auto are more well suited to the 3.6, but that combo flat out works.
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Old 10-31-2013, 10:26 AM   #10
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^Agreed....

If you are ordering a manual, you lack a torque converter....so you should get the 3.73's.

Also, since you are ordering a heavier 4 door, so should get the 3.73's...plus it will bump your tow rating up to 3500 pounds.
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Old 10-31-2013, 10:28 AM   #11
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Personally, I get the deepest factory gears that are available on any vehicle I buy. Made the mistake of buying a Chevy Silverado with 3.42 gears before I knew any better. What an absolute dog! These super tall factory gears are used to squeeze out every last drop of mpg for CAFE standards, nothing else. Cannot imagine driving around with 3.21 gearing, but that's just me. Try 4.10 gears then try 3.21 gears and tell me which is more pleasurable to own and drive.
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Old 10-31-2013, 10:28 AM   #12
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thanks all. A real mixed bag of opinion, but that's OK. I think I'll be sticking with the 3.21, since I don't see ever doing a lift kit or much bigger tires. Thanks
From the many MPG posts on here, the 3.21s do not really benefit in terms of mileage in the real world over the 3.73s. They cause you to downshift more often and lug in non-ideal situations (i.e. hills). There's no reason to get 3.21s, they only cause regret. Unless you live in the flatlands, get the 3.73s. Even in my JKU, i've pulled 20mpg average over 25k miles.
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Old 10-31-2013, 10:38 AM   #13
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And you only get to decide once. Thanks all.
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Old 10-31-2013, 10:39 AM   #14
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If you're planning no tire/lift/suspensions, and aren't doing any SERIOUS offroading, then I think you're OK. I have a JK Sport, 6spd, 3.21 and while I DO have to downshift out of 6th or 5th on these Vermont hills and dirt roads, I enjoy my 22mpg, since it's 16 miles to town, and 28 miles to Home Depot, haircut, WallyWorld, etc.
I also think that you'd be happy if you got 3.73's.....a bit more off the line, with just a small (hardly noticeable) decrease in MPG's.
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Old 10-31-2013, 11:40 AM   #15
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From the many MPG posts on here, the 3.21s do not really benefit in terms of mileage in the real world over the 3.73s. They cause you to downshift more often and lug in non-ideal situations (i.e. hills). There's no reason to get 3.21s, they only cause regret. Unless you live in the flatlands, get the 3.73s. Even in my JKU, i've pulled 20mpg average over 25k miles.
3.21s are crap on gas. They are fine around town, but get on the freeway, and its toast. They are just not enough to push the brick in 5th (auto.) Biggest mistake of my 12 was getting the 3.21s, and the main reason I traded in for the 14. $495 for a regear under warranty is still a great deal compared with what it costs to do aftermarket. OP, if you are ordering, you will regret 3.21s, don't do it.
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Old 10-31-2013, 11:47 AM   #16
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Disagree. My Sahara couldn't stay in ECO mode if I was in 5th and going uphill. I got better MPG in 4th than in 5th. Once I got 33s (32" actual) 5th became useless on everything besides downhills. 4th was useless in Colorado. They are just bad gears, simple as that, and don't belong anywhere near a wrangler. Notice ALL the posts in this thread...AT BEST you hear members say "they are OK." Do you really want something that's just OK?

Also, without getting into which is better manual or auto, consider this...the auto in the wrangler is very stout, well geared, and is considered to be one of the best tried and true automatics. The manual on the other hand is probably one of the worst manual transmissions available on modern automobiles. Im a manual guy, love rowing my own gears, and all my toys (my m3s, my s2000, etc) are/were manual. If you are used to a quality manual transmission, you may not like the Wrangler's...it has a lot of issues as well, and a few drawbacks when it comes to water crossings. Just something to keep in mind.
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Old 10-31-2013, 11:52 AM   #17
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3.21s are crap on gas. They are fine around town, but get on the freeway, and its toast. They are just not enough to push the brick in 5th (auto.) Biggest mistake of my 12 was getting the 3.21s, and the main reason I traded in for the 14. $495 for a regear under warranty is still a great deal compared with what it costs to do aftermarket. OP, if you are ordering, you will regret 3.21s, don't do it.
This x100000

If you are ordering, there is no logical reason not to get the highest numerical value. I regret getting the 3.21s and I have 33s with no plans for 35s. A regear is in my future. It would be in my future even if I was on oem tires.

But hey, if you like having to floor it to keep up with traffic.....
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Old 10-31-2013, 11:54 AM   #18
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This x100000

If you are ordering, there is no logical reason not to get the highest numerical value. I regret getting the 3.21s and I have 33s with no plans for 35s. A regear is in my future. It would be in my future even if I was on oem tires.

But hey, if you like having to floor it to keep up with traffic.....
Agreed. I lost $1800 on my trade in (paid 34K got 32K for trade), and a regear alone would have cost me $1500 in the NJ area. It was a no brainer. I got a brand new Jeep with 4.10 gears for basically the same money.
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Old 10-31-2013, 12:00 PM   #19
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Agreed. I lost $1800 on my trade in (paid 34K got 32K for trade), and a regear alone would have cost me $1500 in the NJ area. It was a no brainer. I got a brand new Jeep with 4.10 gears for basically the same money.
Not bad at all!

On the bright side, when I do regear it will be at least 4.56s

The mpg will certainly improve, since it will be able to pick up and maintain speed with less throttle. That is the primary dictator of mpg. I firmly believe that in most cases the 3.21s are a detriment to fuel economy. RPM are always too low where there is no power and you need to really lay into it to get decent acceleration. I get 16mpg on 3.21s.
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Old 10-31-2013, 12:03 PM   #20
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I have 2013 jku auto with 35" tires and 3:21 gears. I haven't compared it to lower gearing yet, but so far its been fine. No significant difference compared to stock 29" tires. The biggest difference i could notice is bad mpg and longer brake travel. Now, when im on a hilly road then i feel it little over reving, but most roads around here are flat. I might regear down the road, but its definately doable with auto tran.
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Old 10-31-2013, 12:06 PM   #21
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Not bad at all!

On the bright side, when I do regear it will be at least 4.56s

The mpg will certainly improve, since it will be able to pick up and maintain speed with less throttle. That is the primary dictator of mpg. I firmly believe that in most cases the 3.21s are a detriment to fuel economy. I get 16mpg on 3.21s.
Agree 100%. I wasn't able to maintain momentum in 5th without mashing the gas, and on really hilly roads, even in 4th.
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Old 10-31-2013, 12:08 PM   #22
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Disagree. My Sahara couldn't stay in ECO mode if I was in 5th and going uphill. I got better MPG in 4th than in 5th. Once I got 33s (32" actual) 5th became useless on everything besides downhills. 4th was useless in Colorado. They are just bad gears, simple as that, and don't belong anywhere near a wrangler. Notice ALL the posts in this thread...AT BEST you hear members say "they are OK." Do you really want something that's just OK?

Also, without getting into which is better manual or auto, consider this...the auto in the wrangler is very stout, well geared, and is considered to be one of the best tried and true automatics. The manual on the other hand is probably one of the worst manual transmissions available on modern automobiles. Im a manual guy, love rowing my own gears, and all my toys (my m3s, my s2000, etc) are/were manual. If you are used to a quality manual transmission, you may not like the Wrangler's...it has a lot of issues as well, and a few drawbacks when it comes to water crossings. Just something to keep in mind.
First I've heard that the manual isn't a quality manual transmission. Is that real?
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Old 10-31-2013, 12:10 PM   #23
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i have 3.21 on my 12'. 6spd w/ 33's...actually 32's when measured. based on my location...i get great gas mileage around town/highway, but thats all. Life offroad is horrendous as well as climbing mountains. After my purchase, thats when i found out about gearing. There's a possibility that i will be going to the dealer this weekend for a rubi. i couldve saved myself more money by joining wf prior to my purchase.
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Old 10-31-2013, 12:11 PM   #24
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^Agreed....

If you are ordering a manual, you lack a torque converter....so you should get the 3.73's.

Also, since you are ordering a heavier 4 door, so should get the 3.73's...plus it will bump your tow rating up to 3500 pounds.
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Old 10-31-2013, 12:15 PM   #25
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In my opinion the 3.21 wasn't enough for the stock 32s and I have a light 2 door. You need 4 lo for any low speed despite if the terrain is difficult or not. On highway I didn't like it either 6 couldn't hold a hill so you always had to down shift. Now with 35s all that is worse but I have every intention of regearing.
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Old 10-31-2013, 12:16 PM   #26
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I had a 2000 TJ for many years before I bought my JK (2013, Auto, 3.21s), I think my Wrangler hauls ass compared to my old TJ. I don't rock climb, run on mostly flat land (Louisiana), don't tow a boat, and am firmly in middle age. I LOVE my Wrangler like it is, and have no desire to jack it up and mount huge shoes (my wife is barely over 5' and can hardly climb in as it is). When the factory rubber wears out, I will install 265s or maybe 285s, but even at that I am going from a 32" tire to a 33" tire in the case of the 285s.

From my personal experience, a JK w/ auto and 3.21s works great. Get's better than 20mpg on the Interstate too...something my TJ wouldn't do if towed on a trailer.

But then, I'm OBVIOUSLY not a REAL Jeeper.
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Old 10-31-2013, 12:25 PM   #27
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Are you getting 29's or 32's? Much better if you are getting the 29's. I don't know anyone that gets those and keeps them however ...

Look, steady-state, no wind, warm day, flat ground, 75 mph - 3.21's with 32's might do you some good. Other than that, get the 3.73's. So expensive to change afterward.
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Old 10-31-2013, 12:46 PM   #28
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First I've heard that the manual isn't a quality manual transmission. Is that real?
Well....the 6-speed trans was one of many reasons I got rid of my '12. Mine popped out of first and fourth gear all the time, especially when it was cold outside.

Overall, the 5-speed manual I had in my '98 was flawless in comparison. Shifted better, never popped out of gear.
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Old 10-31-2013, 12:51 PM   #29
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3.21s are crap on gas. They are fine around town, but get on the freeway, and its toast. They are just not enough to push the brick in 5th (auto.) Biggest mistake of my 12 was getting the 3.21s, and the main reason I traded in for the 14. $495 for a regear under warranty is still a great deal compared with what it costs to do aftermarket. OP, if you are ordering, you will regret 3.21s, don't do it.
Wait, so what I'm getting from your post is that I can take my Jeep to the dealer and get them to install 3.73 gears as if they were a factory option (at $495)?
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Old 10-31-2013, 12:53 PM   #30
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First I've heard that the manual isn't a quality manual transmission. Is that real?
I don't agree with that... It has long throws, basically feels like a truck transmission. From what he's saying it sounds like the manual is worlds better than the new auto running larger tires.

Unless you spend the extra for the Rubicon, 3.73 is as high as you can go.

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