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Old 12-20-2011, 09:34 AM   #1
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3.21 to 3.73? Much difference?

Hi Everyone,

I just purchased a new 2012 Wrangler Unlimited and love it. It feels great to finally own a Jeep. I had a few questions that I was hoping you could answer. My Jeep came with a 3.21 Rear axle ratio and I was wondering if I should upgrade it to the 3.73 rear axle ratio? If I do an after market mod, how much would it cost and is it worth the upgrade? I want to include a tow package on it... I don't do any towing at all, but I would like that option. Additionally, is the extra torque worth spending the money?

Thanks,
Dave

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Old 12-20-2011, 09:44 AM   #2
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It's expensive to re-gear, stick with what you got unless you are putting larger tires on, in which case you may want to re-gear is up to 4.10 or higher. No worth the money to just go to 3.73

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Old 12-20-2011, 10:07 AM   #3
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Go drive one at the dealer with 3.73 before spending all the money to upgrade.
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Old 12-20-2011, 10:25 AM   #4
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Quote:
Originally Posted by ShoreWrangler View Post
It's expensive to re-gear, stick with what you got unless you are putting larger tires on, in which case you may want to re-gear is up to 4.10 or higher. No worth the money to just go to 3.73
Wound a jeep with the 3.73 be able to handle 34s or 35s or would you have to upgrade to the 4.1?
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Old 12-20-2011, 10:28 AM   #5
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Originally Posted by JMC03

Wound a jeep with the 3.73 be able to handle 34s or 35s or would you have to upgrade to the 4.1?
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Old 12-20-2011, 10:48 AM   #6
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Wound a jeep with the 3.73 be able to handle 34s or 35s or would you have to upgrade to the 4.1?
My understanding of it is you would want a 4.10 or higher if you go to 35's, but 33's are ok on 3.73 gearing

34 is a number I have never heard talked about, seems to be 33 or 35's
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Old 12-21-2011, 05:25 PM   #7
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ShoreWrangler & Ranjr,

Thanks for replying to my post. I am kicking myself right now for not ordering my Jeep with a Max Tow Package just to get the 3.73 rear axle ratio. I don't foresee myself doing much towing but I would like to have the extra torque to drive in the mountains in snow, etc... In your opinion, do you think the 3.21 is sufficient or should I look into regearing in the future...perhaps to a higher ratio like 4.10? I'm new to the Wrangler stuff so I apologize for my limited knowledge in this area.

Thanks again!
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Old 12-21-2011, 05:30 PM   #8
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Dude don't worry about it. You've got plenty of power and regardless of which trans you should be fine up to 32's. If it's running fine for your purposes and doesn't seem to require too much shifting or inadequate power there is no reason to change anything. Really.
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Old 12-21-2011, 05:46 PM   #9
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I have a '12 JK with the 3.21 with stock 32" tires and have been pretty happy. If I am on a state route where the speed limit is 55, I use the stick feature to limit the drive to 4th gear. But when I am on a flat Interstate going 70+, I am happy that I have the 3.21. I do tow, so if I had an unlimited I would have gotten the 3.73 to have the 3,500lb capability.
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Old 12-21-2011, 05:52 PM   #10
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Quote:
Originally Posted by SnowboardDEN View Post
ShoreWrangler & Ranjr,

Thanks for replying to my post. I am kicking myself right now for not ordering my Jeep with a Max Tow Package just to get the 3.73 rear axle ratio. I don't foresee myself doing much towing but I would like to have the extra torque to drive in the mountains in snow, etc... In your opinion, do you think the 3.21 is sufficient or should I look into regearing in the future...perhaps to a higher ratio like 4.10? I'm new to the Wrangler stuff so I apologize for my limited knowledge in this area.

Thanks again!
Don't worry about it. If your Jeep drives fine, then it drives fine.
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Old 12-21-2011, 07:21 PM   #11
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Yeah, don't sweat the gears. It's easy to come on these sites and read everyone's comments about "needing" the lower gear ratios. Fact is, you only need what you need. Drive with the 3.21s for a while and see if it does everything you need it to. If later down the road you decide to run larger tires, try it with the 3.21s and make the upgrade choice based on your experience.

Don't just run out and spend the money upgrading gears because some on the Internet say its required. Remember the majority of those insisting on the lower gears have the '07-'11 JKs with the terrible ratio 4 speed Auto. The 2012 Pentastar and 5 speed Auto is rewriting what's required for gears.
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Old 12-21-2011, 07:44 PM   #12
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Quote:
Originally Posted by SnowboardDEN View Post
Hi Everyone,

I just purchased a new 2012 Wrangler Unlimited and love it. It feels great to finally own a Jeep. I had a few questions that I was hoping you could answer. My Jeep came with a 3.21 Rear axle ratio and I was wondering if I should upgrade it to the 3.73 rear axle ratio? If I do an after market mod, how much would it cost and is it worth the upgrade? I want to include a tow package on it... I don't do any towing at all, but I would like that option. Additionally, is the extra torque worth spending the money?

Thanks,
Dave
See post below. You don't need to regear on the '12 unless you plan on adding tires over 33", or towing close to max capacity. You'll notice a bit of power loss when passing on the highway or going up steep hills, but not too bad.

Quote:
Originally Posted by ShoreWrangler View Post
It's expensive to re-gear, stick with what you got unless you are putting larger tires on, in which case you may want to re-gear is up to 4.10 or higher. No worth the money to just go to 3.73
Yup. Good advice.

Quote:
Originally Posted by JMC03 View Post
Wound a jeep with the 3.73 be able to handle 34s or 35s or would you have to upgrade to the 4.1?
If you've got a '12, you'll wanna regear if you're running 35's (which for most tires is actually 34"). I'm running a '12 with 3.73's and 35's, and notice a marked difference in 6th gear (manual) on the highway, and when climbing hills. I'll be getting 4.88's in the near future.

Quote:
Originally Posted by ShoreWrangler View Post
My understanding of it is you would want a 4.10 or higher if you go to 35's, but 33's are ok on 3.73 gearing

From my experience, you should be okay with 3.73's and 33's on a '12. Not ideal, but possibly not worth the $1500 it'd cost to regear. I've got 3.73's and 35's, and feel the pain only on the freeway in 6th, and on hills.

34 is a number I have never heard talked about, seems to be 33 or 35's
Many tires are less than the 33 or 35 designation. My "35" inch DuraTracs are actually 34.6 inches, which is a better "advertised-to-reality" ratio than most.
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Old 12-21-2011, 07:50 PM   #13
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If you do much Interstate driving you will be pleased when you set the cruise control on 70mph and see the average mpg hit 23 or so.
I have the 3.73 on my 2012 and get about 20mph on the Interstate. I am there more than I am on the trails.
For the serious stuff I drive my CJ-7.
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Old 12-21-2011, 07:58 PM   #14
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you're getting some good answers here
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Old 12-21-2011, 08:13 PM   #15
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not trying to compare oranges and apples--but I have 3.73s in my TJ. My 2012 JK auto has the 3.21s.

I realize the JK has way more ponies and the auto in the JK vs. stick in the TJ. Yes for off road when I do go to 33s in the TJ I will be re-gearing.

Granted I only have just over 500 miles on the JK but most were on the highway, and I love the gas mileage, and power that is there. I will have to really be doing some serious wheeling in the JK before I would consider a regear for it.

I believe the factory set-up will be more than adequate for any bad roads or weather that I may run into.
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Old 12-21-2011, 09:24 PM   #16
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I choose the 3.73 because it gives you more options. Towing, adding bigger tires....

As far MPGs go. I maxed out at 22 MPG on the HWY using cruise.

Test drive both.
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Old 12-21-2011, 10:50 PM   #17
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My 2012 Sport came with the stock 16" wheels with hiway tires. It also had the 3.73 gears and the automatic transmision.
At 70mph the rpm was 2650-2700 rpm and out of the green zone for good gas mileage. After putting on the BFG AT 32x11.5-15 on MB72 rims, rpm was now 2350 at 70mph and I improved gas mileage by 2mpg.
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Old 12-22-2011, 10:37 AM   #18
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Quote:
Originally Posted by 71K5
My 2012 Sport came with the stock 16" wheels with hiway tires. It also had the 3.73 gears and the automatic transmision.
At 70mph the rpm was 2650-2700 rpm and out of the green zone for good gas mileage. After putting on the BFG AT 32x11.5-15 on MB72 rims, rpm was now 2350 at 70mph and I improved gas mileage by 2mpg.
Did you adjust the speedometer/odometer after adding the larger tires?
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Old 12-22-2011, 12:00 PM   #19
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Did you adjust the speedometer/odometer after adding the larger tires?
Yes, see my post on the following "city mileage" thread link.
http://www.wranglerforum.com/f33/cit...-128685-2.html
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Old 12-22-2011, 12:22 PM   #20
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not trying to compare oranges and apples--but I have 3.73s in my TJ. My 2012 JK auto has the 3.21s.

I realize the JK has way more ponies and the auto in the JK vs. stick in the TJ. Yes for off road when I do go to 33s in the TJ I will be re-gearing.

Granted I only have just over 500 miles on the JK but most were on the highway, and I love the gas mileage, and power that is there. I will have to really be doing some serious wheeling in the JK before I would consider a regear for it.

I believe the factory set-up will be more than adequate for any bad roads or weather that I may run into.
It IS oranges and apples, however. Your '12 JK will run perfectly well with the 3.21's (though why you allowed them to be installed on your Jeep when you could've gotten 3.73's for an extra $50 completely baffles me). As long as you run tires 33" or under.

Go to 35's, and you'll see a marked difference, especially if you've been driving your '12 stock for awhile.

Not being an a** here, just pointing out that the '12, even with it's world-saving engine, has limitations similar to all Jeeps.
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Old 12-22-2011, 04:20 PM   #21
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It IS oranges and apples, however. Your '12 JK will run perfectly well with the 3.21's (though why you allowed them to be installed on your Jeep when you could've gotten 3.73's for an extra $50 completely baffles me). As long as you run tires 33" or under.

Go to 35's, and you'll see a marked difference, especially if you've been driving your '12 stock for awhile.

Not being an a** here, just pointing out that the '12, even with it's world-saving engine, has limitations similar to all Jeeps.
I didn't order my Jeep--I was looking for a better vehicle for winter for my sig other--she has an old Camry with a bad front end--saw the one that fit price point and options on the lot coming home after work and signed the papers about an hour later. She didn't even know till the deal was done.
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Old 12-22-2011, 05:20 PM   #22
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I didn't order my Jeep--I was looking for a better vehicle for winter for my sig other--she has an old Camry with a bad front end--saw the one that fit price point and options on the lot coming home after work and signed the papers about an hour later. She didn't even know till the deal was done.
Early Christmas? Sweet!
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Old 12-22-2011, 05:29 PM   #23
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Question

I just bought a 2008 Wrangler, and it of course didn't come with a build sheet or window sticker since it is used. How do I know which axle ratio mine is? I am wanting to do aftermarket stuff to it and the company is asking which mine has!

I know that is aweful that I do not know
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Old 12-23-2011, 05:24 AM   #24
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Early Christmas? Sweet!
Yeah pretty much early everything....Christmas/Valentine's/Birthday...I should be good for a while..and it is way easier for mods as they are on "her" Jeep
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Old 12-23-2011, 06:11 AM   #25
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ShoreWrangler & Ranjr,

Thanks for replying to my post. I am kicking myself right now for not ordering my Jeep with a Max Tow Package just to get the 3.73 rear axle ratio. I don't foresee myself doing much towing but I would like to have the extra torque to drive in the mountains in snow, etc... In your opinion, do you think the 3.21 is sufficient or should I look into regearing in the future...perhaps to a higher ratio like 4.10? I'm new to the Wrangler stuff so I apologize for my limited knowledge in this area.

Thanks again!
That is exactly what I did. I test drove one with 3.21s and decided I'd be
happier with 3.73s. And I do tow occasionally. So I had the dealer find one with the max tow package. Very happy here so far.
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Old 12-23-2011, 07:16 AM   #26
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Thanks for all the posts! I appreciate the realistic, down-to-earth feedback!!! It was my mistake that I didn't research the axle ratio before purchasing my Jeep. My initial thinking was that I wanted to maximize on MPG but now realize that the cost/benifit ratio between the 3.73's and MPG is somewhat negligable. However, for the type and style driving I will be utilizing the JK '12 for, the 3.21's should do just fine. Thanks again for all the help!

BTW-I will be installing an after market hitch...mostly so that I can add a bike rack or ski/snowboard carrier. Any recommendations there? Quadratec has several...or go with the one the dealer has? My max tow is 2,000 so I don't need anything crazy...but versatile is good. Have an awesome Holiday season everyone!
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Old 12-23-2011, 09:11 AM   #27
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Not sure on the hitch. But I love my spare tire mounted bike rack. I never have to take it off. Although, I did take it off for the winter. Thule Spare Me 2 Spare Tire Carrier - Bike from Backcountry.com

This link is for information, I don't think it is the cheapest site.
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Old 12-23-2011, 10:53 AM   #28
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Hey SnowboardDen:

Do you have an auto or manual transmission.

If you have the manual with 3.21 gears, then you have a better 4lo crawl ratio than an Auto with 3.73 gears. So if you have a manual you should be fine.
Manual Transmission Crawl ratio=4.46(1st gear)x2.72(t-case)x3.21=38.94
Auto Transmission Crawl ratio=3.59(1st gear)x2.72 x 3.73= 36.42

Manual Gears: 4.46(1); 2.61(2); 1.72(3); 1.25(4); 1(5); .797(6)
Auto Gears: 3.59(1); 2.19(2); 1.41(3); 1(4); .83(5)

So by the gear ratios it should tow as well as or better than an automatic with 3.73 gears.

But if you have an automatic with 3.21 gears and the Unlimited 4dr, I would not excede 2000lbs.

I have a Curt hitch and it has really thick powder coat paint that is baked on. Excellent quality.

If anyone wants to calculate the other crawl ratio combinations, just swap in the Rubi T-case ratio of 4.0 into the calculations, as well as it's 4.1 available axle ratio.

Max crawl is Rubi Manual with 4.1 gears at 73.1.
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Old 12-23-2011, 12:11 PM   #29
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Hey SnowboardDen:

Do you have an auto or manual transmission.

If you have the manual with 3.21 gears, then you have a better 4lo crawl ratio than an Auto with 3.73 gears. So if you have a manual you should be fine.
Manual Transmission Crawl ratio=4.46(1st gear)x2.72(t-case)x3.21=38.94
Auto Transmission Crawl ratio=3.59(1st gear)x2.72 x 3.73= 36.42

Manual Gears: 4.46(1); 2.61(2); 1.72(3); 1.25(4); 1(5); .797(6)
Auto Gears: 3.59(1); 2.19(2); 1.41(3); 1(4); .83(5)

So by the gear ratios it should tow as well as or better than an automatic with 3.73 gears.

But if you have an automatic with 3.21 gears and the Unlimited 4dr, I would not excede 2000lbs.

I have a Curt hitch and it has really thick powder coat paint that is baked on. Excellent quality.

If anyone wants to calculate the other crawl ratio combinations, just swap in the Rubi T-case ratio of 4.0 into the calculations, as well as it's 4.1 available axle ratio.

Max crawl is Rubi Manual with 4.1 gears at 73.1.
From what I understand, you can't directly compare the crawl ratio of an auto with a manual. The torque converter allows slippage and has a torque amplification effect which improves the effective crawl ratio versus a manual transmission.

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