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Old 01-29-2012, 07:54 AM   #1
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2012 Sport 3.21 vs 3.73

My 2012 Unlimited Sport has the 3.21 gears in it. I have concerns that this will not be acceptable for running 33's. A few threads I have found say this is not as much of an issue on the 2012 with the 5-speed auto.

I'm already talking to my dealer about ordering one with 3.73 gears in it. Would it be worth it to go ahead and trade? Or should I stick with the 3.21?

I won't be going any bigger than 33's. I ran 33's on my 2010 JKU and it worked out great with the 3.73 gears.

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Old 01-29-2012, 08:05 AM   #2
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Oooo thats a tuffy guy.

After testing a jk with 3.21's, i was like where is all this added
Power?? Then I went searching for the 3.73's,,,..

And I was really shocked how it pushed me back in my seat gunning it on the interstae!!!

I then said,, a few other moments,, this jeep kinda has some balls now!!!

3.73's make alot of difference.

I can see how someone could make a mistake,, of the 30+ wranglers in my area for sale,,only 2 had 3.73's!!

Im about to buy one of them!,,,

Best of luck to ya

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Old 01-29-2012, 08:08 AM   #3
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IDK---but things to consider------I have a '04 TJ Sport with 3.73's that works fine with 31's. (this was not the factory size) Where am I going with this? I had/ and have never had any problem running this in snow, mud or on the highway. Everyone tells me I need/ or will need to re-gear for mud and everything else or it will not perform correctly. It works for me. MAYBE if and when I go to 33's it will be a problem--I will wait and see.

I recently purchased a '12 JK Sport--with the 3.21's and it is more than better than the TJ ever thought about being in the snow, with 32's on it and the auto. It really shines on the highway and mileage is unbelievable IMO!

Bottom line IDK if I would go looking to order a different Jeep based on what people are saying. Try the 33's and than if you "need to trade" pull the 33's off and trade put the 33's on new Jeep. I doubt you will find it a "need" to trade for 3.73's.

However your more hilly terrain may make a difference.

Good LUCK!!
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Old 01-29-2012, 08:21 AM   #4
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After driving another 2012 with 3.73 gears in it, I agree that there was a big difference in power. And I know that the torque in my 2012 with 3.21 gears is higher than it was with my 2010 with 3.73. And considering that the tire/wheel combo I will be running will be lighter than the stock 32's I'm running now, maybe I should just run it like it is.

My dealer is willing to order one and trade with minimal cost difference. Just trying to figure out if it's worth the effort.
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Old 01-29-2012, 09:47 AM   #5
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3.21's are usually new lot vehicle's for clueless buyers.
One positive is- listed mpg's..... Maybe
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Old 01-29-2012, 11:42 AM   #6
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Get the 3.73's now for minimal cost, or pay roughly $1500 to change them out down the road.

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Old 01-29-2012, 11:46 AM   #7
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Yep do the trade now

It will be a load off your mind

And extra power under your butt!!!

I was really shocked how it set me back in my seat and then continued to scoot away from like 4k - to shift point
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Old 01-29-2012, 11:53 AM   #8
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3.21s are purely a stock/highway gear. Get the 3.73s and limited slip.

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Old 01-29-2012, 12:25 PM   #9
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Thanks for the input. I am going to go with the trade. They are going to order it tomorrow so I'll have the usual delays. But I think it will be worth it in the long run.
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Old 01-29-2012, 12:26 PM   #10
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The Sport S comes with 3.21s? Only the "towing package" has the 3.73s? I have 33s and haven't had a problem.
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Old 01-29-2012, 02:21 PM   #11
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I wouldn't think it would be that big of a deal running 33's. That said, I do have the 3.73 gears (max tow) with 33's.

I don't know how much it would cost you to get a new one with the 3.73, but sounds like a salesmans dream come true making a 2nd commission.

I would just throw the 33's on and see how you like it. Then use an AEV Procal to correct the settings. If you still don't like it, you could put the wheels on the new one. It just seems like with the added horsepower, 33's would be fine. If you don't like it, then consider the trade and get them to subtract money for the wheels.
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Old 01-29-2012, 02:25 PM   #12
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I don't know any dealers that are this cool. Gear swap is 1500, I would imagine it isn't a straight trade or a few bucks more... They have to make it worth their time to do something like this.
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Old 01-29-2012, 02:36 PM   #13
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It was their mistake to begin with. I specified 3.73. They found this one on a dealer trade. I questioned it from the day I picked it up. I've bought 10 vehicles at this dealership and wouldn't consider going anywhere else.
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Old 01-29-2012, 04:07 PM   #14
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I think you're making a big deal out of nothing. Slap some 33s on it and drive it. There are guys running 35s with the auto and 3.21s with no issues.

Believe it or not, the 3.21 will be quicker on the interstate when you floor it because it will downshift to 2nd gear where the 3.73 and 4.10 will only hit 3rd.
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Old 01-29-2012, 04:15 PM   #15
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I have 3:21 and 33's on my 2012 and there was no difference when I switched from stock tires to my 33 Duratracs. Not a bit.

With that said, I wish I had the 3:73. I also wish I had a standard & not an automatic but I had to buy off the lot & in a hurry so I didn't have much choice.

And I also do not have an unlimited...
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Old 01-29-2012, 06:05 PM   #16
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Quote:
Originally Posted by ranjr
I think you're making a big deal out of nothing. Slap some 33s on it and drive it. There are guys running 35s with the auto and 3.21s with no issues.
This. I have a 2010 with 3.21s and a lightweight 33" set up. It's fine. No detectable difference from stock. If that's the case with a 2010, I'm confident your 2012 will be fine. Taking a multi-thousand dollar hit on a trade to "remedy" this "problem" is insane. You surely would've been better off with 3.73s, but you don't suddenly need to get rid of your jeep.
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Old 01-29-2012, 06:15 PM   #17
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Don't believe everything you read in this thread and take it at face value, as your experience will vary.

When people talk about performance with gears and a certain tire size you need to take in account their terrain (flat or hilly), driving conditions (city or highway), altitude (sea level or mountain), use (street or offroad, towing or hauling), as well as their previous experience. All of this comes in to play in the outcome and expectations. With a 5-speed auto and its wide gear spread, in my opinion it is safer to over gear (3.73) than to under gear (3.21).

Only those with similar situations are comparable to what you will experience. There are just too many variables to listen to the one guy that tells you it will be fine with no details to support his comment.

That being said, I ordered mine with 3.21s because I knew I would swap the gears out. I was pleasantly surprised with how well the new engine and 3.21s felt stock, totally acceptable. However, I wouldn't run anything over a 33 with 3.21s, it already turns slow enough at highway speeds and you won't have enough power if you plan on doing any serious wheeling. I can't imagine wheeling where I do with 35s and 3.21s, but I can see how a Jeep at sea level or flat terrain that was only going to be used on the pavement would be fine.

My advice would be to keep your Jeep if the only issue is gearing and put the 33s on. If it feels sluggish, then do a gear swap for about $1000 and help the drivetrain and your butt dyno out. I wouldn't buy a new Jeep, that seems silly when the problem can be easily fixed on yours in an afternoon.

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Old 01-29-2012, 06:20 PM   #18
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Quote:
Originally Posted by Sueby
I have 3:21 and 33's on my 2012 and there was no difference when I switched from stock tires to my 33 Duratracs. Not a bit.

With that said, I wish I had the 3:73. I also wish I had a standard & not an automatic but I had to buy off the lot & in a hurry so I didn't have much choice.

And I also do not have an unlimited...
I feel the same way. Buyers remorse about not getting 3.73 gears. But really it drives fine with the 32s on it. And I am not unhappy with the mileage. First tank I got 16.5 around town. Wish I had the manual too but, the other half wont learn how to drive one.
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Old 01-29-2012, 06:38 PM   #19
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Originally Posted by seanpholman
With a 5-speed auto and its wide gear spread, in my opinion it is safer to over gear (3.73) than to under gear (3.21).
Actually the gear spread on the 5 speed is closer than the 4 speed; 1.0 4th to .84 5th vs 1.0 3rd to .69 4th. One of the big advantages is the small jump in RPM from O/D to D of 3-400 RPM where the old 4 speed would jump nearly 1000 RPM. It's not as big a deal to drop out of O/D now.
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Old 01-29-2012, 06:49 PM   #20
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Look at the entire picture, 1st is now 3.59 with the WA580 compared to 2.84 with the 42RFE. It is the ratios down low that give you the flexibility for running larger tires.

1st: 3.59 vs. 2.84
2nd: 2.19 vs. 1.57
3rd: 1.41 vs. 1.00
4th: 1.00 vs. .69
5th: .83 vs. ---

As you mentioned above, having the extra cog does make the shift from D to O/D much more reasonable and with a shorter O/D gear, it gives you a few hundred RPM of cushion as not to lug the engine with bigger tires.

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Old 01-29-2012, 07:04 PM   #21
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Nobody ever complains of not enough power in the lower gears. It's all in how it drives on the highway and weather or not it will hold O/D.
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Old 01-29-2012, 07:06 PM   #22
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Regear to 4:10's problem solved plus some ?
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Old 01-29-2012, 07:11 PM   #23
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Nobody ever complains of not enough power in the lower gears. It's all in how it drives on the highway and weather or not it will hold O/D.
Wow, talk about painting with broad strokes. Power in low gears is just as important on the highway, especially for a Jeep customer. As I am sure you know, gearing is a delicate balance, but I know plenty of people not happy with their 4x4 off the line after adding larger tires and not regearing.

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Old 01-29-2012, 07:11 PM   #24
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Regear to 4:10's problem solved plus some ?
Sure, depends on the tire size.

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Old 01-29-2012, 07:14 PM   #25
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So how much is it going to cost you for the trade? I would assume, and I could so be totally wrong, that it would cost you more than just regearing in the end. No?

And if not, are you happy with your current ride? If you are and you don't plan on towing anything or doing any good wheeling and only plan on adding 33's, is it really worth the hassle? Like I said there was 0 difference with the 33's from stock.

Course if it's not going to cost you anything because the dealer screwed up - then go for it!
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Old 01-29-2012, 07:24 PM   #26
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Wow, talk about painting with broad strokes.

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Why do you think the gear charts show RPM for a given tire diameter and rear end ratio at 70 MPH in O/D? Last I checked, you don't run 70 in 1st or 2nd.
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Old 01-29-2012, 07:42 PM   #27
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So how much is it going to cost you for the trade? I would assume, and I could so be totally wrong, that it would cost you more than just regearing in the end. No?

And if not, are you happy with your current ride? If you are and you don't plan on towing anything or doing any good wheeling and only plan on adding 33's, is it really worth the hassle? Like I said there was 0 difference with the 33's from stock.

Course if it's not going to cost you anything because the dealer screwed up - then go for it!
It's not going to cost me anything other than a few other things we added. The dealer is going above and beyond. If this was going to be something that I was going out of pocket too much, I would have just went ahead and re-geared at a later date.

I realize that around town and on the highway the difference would not be noticeable. But I do spend a lot of time in the mountains up in Colorado. That is where I fear I would be kicking myself.
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Old 01-29-2012, 07:51 PM   #28
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It isn't as cut and dry as that. Charts aren't the end all be all, they are just a guide or a reference point. You still need to figure into the equation all of the things I listed above (tire size, use, altitude, type of terrain, weight, cruising speed, etc.) to match the right gear with the right driver. Hopefully there is enough info here to help the OP and anyone else reading this make an educated decision and that is all that matters.

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Old 01-29-2012, 07:52 PM   #29
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It's not going to cost me anything other than a few other things we added. The dealer is going above and beyond. If this was going to be something that I was going out of pocket too much, I would have just went ahead and re-geared at a later date.

I realize that around town and on the highway the difference would not be noticeable. But I do spend a lot of time in the mountains up in Colorado. That is where I fear I would be kicking myself.
Okay, that makes sense then. And I do agree that in the mountains you would be kicking yourself. Sounds to me that you are making the right call.

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Old 01-29-2012, 08:33 PM   #30
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Heck yea, if it's not costing you anything go for it!

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