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Guys, I am getting ready to buy a new 2013 Jeep, I want a base model sport that I can upgrade myself, I have been looking at several base sport models with 3.73 gearing but I have found a few with 3.21 that I can get for $20,000 flat. Wanted your thoughts, I will be upgrading the tires and rims to 15" rims with 33x12.5 tires. Will not be doing any heavy off roading just logging roads and hunting trails do you think the 3.21 will be a big deal.
 

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rlpickering13 said:
Guys, I am getting ready to buy a new 2013 Jeep, I want a base model sport that I can upgrade myself, I have been looking at several base sport models with 3.73 gearing but I have found a few with 3.21 that I can get for $20,000 flat. Wanted your thoughts, I will be upgrading the tires and rims to 15" rims with 33x12.5 tires. Will not be doing any heavy off roading just logging roads and hunting trails do you think the 3.21 will be a big deal.
3.21 gearing, from what ive been reading for the last year, will be totally fine with 33" tires. 3.73 would be better, but for 33" tires and the new Pentastar Engine, your set. The general rule is: 31-33" (3.23-3.73) 35(4.57 and up)
 

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You'll be getting into the range where you want to consider an upgrade. I've got a stock sport with the S package and the 255/75R17 tires (32.1" diameter"). I can get around just fine. The 33's will usually measure just under 33" (probably 32.6-32.8 depending on the brand).

I have no trouble getting around but when there's a good headwind on the freeway I find myself downshifting to 5th more often than I have with any other vehicle.

The 3.73's would be better but for the difference in the off-the-lot price you may be able to drop money on lockers and gears at the same time and come out ahead.
 

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3.21s will be perfectly fine for 33s. I'd still suggest waiting on 3.73s/paying more unless you are ABSOLUTELY certain you'll never go larger tire/do more mods. Got a great deal on my 3.21s but regret it..in the end I'll probably pay the same due to re-gear.
Said before and one more time- think of 3.73s as insurance against the costly, easily transferrable and highly contagious Jeep mod. bug.
(Search "3.21" in the forum search tool for more info. on 3.21s- Many threads).
 

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This topic comes up all the time. It should really be a sticky, as this question gets fielded constantly.

That said, here's my syllogism:

(1) If the cost is the same, you would never deliberately choose 3.21s, as 3.73s are better in every conceivable category except perhaps a slight (slight) improvement in gas mileage with the 3.21s on flat surfaces.

(2) The cost of upgrading your gears aftermarket will be somewhere around $1200 to $2000, and runs the risk of compromising some of your drivetrain warranty.

(3) 3.21s will work. Lots of people have them.

Therefore . . .

Unless you're getting a discount of $2000 dollars or so, you should choose 3.73s.
 

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This topic comes up all the time. It should really be a sticky, as this question gets fielded constantly.

That said, here's my syllogism:

(1) If the cost is the same, you would never deliberately choose 3.21s, as 3.73s are better in every conceivable category except perhaps a slight (slight) improvement in gas mileage with the 3.21s on flat surfaces.

(2) The cost of upgrading your gears aftermarket will be somewhere around $1200 to $2000, and runs the risk of compromising some of your drivetrain warranty.

(3) 3.21s will work. Lots of people have them.

Therefore . . .

Unless you're getting a discount of $2000 dollars or so, you should choose 3.73s.
^^^This

3.21s are perfectly fine with 33's. I have zero issues running 33's along with many others on here.

Good Luck :thumb:
 

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If one was to upgrade from 3.21 to 3.73 or higher. Would you have to change the differential housing? And do you re-gear both front & rear?

I have 3.21 & I believe it is lagging my jeep at times. When I make U-turns, going up hills, trying to make it go fast.
 

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If one was to upgrade from 3.21 to 3.73 or higher. Would you have to change the differential housing? And do you re-gear both front & rear?

I have 3.21 & I believe it is lagging my jeep at times. When I make U-turns, going up hills, trying to make it go fast.
The axle housing itself does not have to be changed to change gears.

If you upgrade to anything between 3.21 and 3.54, you only have to change the ring and pinion along with the install kit that goes with it.

Once you go above 3.54, you have to change out the carrier in the front axle. Once you go above 3.73, you have to change out the carrier in the rear axle.

You technically don't HAVE to change out the gears at the same time. But if you put it into 4WD with gears that don't match you'll break something pretty quickly. For all intents and purposes there's no good reason to change gears in just one axle. If you can't afford to do both, wait and save up until you can.
 

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You won't be able to run 15" wheels on your 2013. The brake calipers are to big. Some aftermarket 16" wheels won't fit either even though the sport comes with 16" wheels.
 

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You won't be able to run 15" wheels on your 2013. The brake calipers are to big. Some aftermarket 16" wheels won't fit either even though the sport comes with 16" wheels.
They put bigger calipers on the 2013's then what they used for 07-12?
 

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Schott216 said:
You won't be able to run 15" wheels on your 2013. The brake calipers are to big. Some aftermarket 16" wheels won't fit either even though the sport comes with 16" wheels.
XJ Knight said:
They put bigger calipers on the 2013's then what they used for 07-12?
I think the calipers are the same--Schott216, I believe you're incorrect, at least in the US. Some 15" wheels fit, and all 16" wheels fit. Tire shops that tell you different are just wrong. (I actually have 15" wheels on my 2010 JKU.)
 

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So, safe bet is just to replace everything there when upgrading on both!

The axle housing itself does not have to be changed to change gears.

If you upgrade to anything between 3.21 and 3.54, you only have to change the ring and pinion along with the install kit that goes with it.

Once you go above 3.54, you have to change out the carrier in the front axle. Once you go above 3.73, you have to change out the carrier in the rear axle.

You technically don't HAVE to change out the gears at the same time. But if you put it into 4WD with gears that don't match you'll break something pretty quickly. For all intents and purposes there's no good reason to change gears in just one axle. If you can't afford to do both, wait and save up until you can.
 

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So, safe bet is just to replace everything there when upgrading on both!
I wouldn't change out parts that don't need changing out.

If you're not crossing a carrier break and you don't want to change out from the carrier you have (open or limited slip), there's no reason to replace it unless it's damaged in some way.
 

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I ordered my 13 with 3.73 cause I was going to run 33's and glad I did. It works well but I know I wouldn't have been happy with 3.21's and 33's. 15" wheels fit the 13's I have them on mine. Btw I'm getting avg. 18 mpg on the first two tanks not much highway use so far. I was getting avg. 14.5 mpg with my 01 Sahara with 32's I traded.
 

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I don't see why you can't just drop a gear if you need it. I like the idea of 3.21's and stock tires. I'm thinking about buying a 2013 for a plow vehicle. I also want locking differentials, and figure I can always drop to 4Low. Most plow guys like to back up fast. My plan is to do something radical only a Jeep can do--turn around! Any comments on using 3.21's for plowing? Anyone doing it?

Plowing is a winter sport!
 

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NightSailor said:
I don't see why you can't just drop a gear if you need it. I like the idea of 3.21's and stock tires. I'm thinking about buying a 2013 for a plow vehicle. I also want locking differentials, and figure I can always drop to 4Low. Most plow guys like to back up fast. My plan is to do something radical only a Jeep can do--turn around! Any comments on using 3.21's for plowing? Anyone doing it?

Plowing is a winter sport!
Why do that? Good gears are not just about keeping RPMs in a good spot while cruising--deeper gears give you better starts too, as you'll lug less. I can't think of any reason why you'd choose numerically low gears for something torquey like plowing.

And anyway, the only jeep that comes with locking diffs is a rubicon, which means 3.73 is as numerically low as you can go. 4.10s--a rubicon option--would be better.
 
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