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Old 11-26-2019, 06:35 PM
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Which lockers for a JK Sport with 3.21 Gears

Hello,

Which lockers should I buy - have a Sport S automatic (with 3.21 gears). Tired of constant auto shifting on hills. Might upgrade to 33s someday (no lift now). Thinking 4.56? Any brand better than another?

WRT lockers, I see "27 spline" "30 spline" etc. Which do I use for a stock Sport S with D30F and D44R?

Thank you in advance.

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Old 11-26-2019, 06:54 PM   #2
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Do you mean gears?

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Old 11-26-2019, 07:00 PM
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sorry, gears and lockers
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Old 11-27-2019, 09:04 AM   #4
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What size tires are you running? What year jeep? Auto or manual? Use the calculator here to begin the process. Gear Ratio Calculator

On the D30 I wouldn't recommend going over a 4.56. FWIW - I run 37's on 4.56 gears.

Your D30 front axles shafts are 27 spline. Your D44 rear axle shafts are 30 spline.

Based on my experience, I would recommend you look at the Eston Detroit TruTrac for a traction aid. They are about 1/2 the cost of a locker and provide excellent all wheel traction on and off road.
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Old 11-27-2019, 10:23 AM   #5
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Hello,

Which lockers should I buy - have a Sport S automatic (with 3.21 gears). Tired of constant auto shifting on hills. Might upgrade to 33s someday (no lift now). Thinking 4.56? Any brand better than another?

WRT lockers, I see "27 spline" "30 spline" etc. Which do I use for a stock Sport S with D30F and D44R?

Thank you in advance.
oh, That's the easy part... If you don't know about doing this stuff yourself. Take it to a local shop you trust and tell them what you have *make, model, and year* and then tell them what size tires you plan on running. They then know which spline and what gear selection to install for you. FYI, going from a 3.21 to a lower gear option will require a new carrier up front. Allot of folks suggest NOT locking the front dana 30. I have known a couple that wheel just fine with it locked..and I have also seen folks that tear them up quickly, specially if you don't know when you should be locked or not. If you don't plan on going over 33s go with a 4.10 or even the 3.73s would be good. If you plan on eventually putting a set of 35s then go with your 4.56s and enjoy it.
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Old 11-27-2019, 10:31 AM   #6
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Which lockers for a JK Sport with 3.21 Gears

Regearing and lockers on a D30 is money down the drain. Use the money and buy an aftermarket D44. Look around on CL. I sold my PR44 for a great price with only 10K miles on it. Guy that bought it lives in Minnesota and we shipped it from Arizona.
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Old 11-27-2019, 11:04 AM   #7
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Regearing and lockers on a D30 is money down the drain. Use the money and buy an aftermarket D44. Look around on CL. I sold my PR44 for a great price with only 10K miles on it. Guy that bought it lives in Minnesota and we shipped it from Arizona.
Depends on what his long term plans are and how he uses his Jeep.Not everyone who wishes a traction device have a need for a Dana 44.

If 33's are as large of a tire he plans to use and he isn't banging around in rocks, 4.56 gears on a D30 is fine. It's not a waste of money, putting in the right gears for the tires and a traction device is smart and a D30 can handle these mods just fine in low to moderate off road use. Regearing gives him back the performance that is lost when leaving stock tire sizes.

If the use case is more geared to semi serious/serious off road use, then absolutely, save up for a Rubicon D44/Ultimate 44/Core 44/Prorock 44 or Rockjock 44
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Old 11-27-2019, 11:48 AM   #8
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As cranbiz said, which gears are mainly a question of which tires you want to run. For 32" - 33" tires and the 3.6 motor 4.56 gears are common and work well. For the older 3.8 motor you may want 4.88 or even 5.13 gears for that same tire size, depend on trans and how you drive.
As to traction enhancement, I am a fan of a mechanical LSD like a TrueTrac in the back and either a TrueTrac or select-able locker up front. Lockers front and rear are OK, but for most I think a mechanical LSD in the back is more useful (unless you are building a hard core rock crawler).
Typically you have a shop do the gears, as they take some special tools and knowledge to do right. So normally you would buy the gears through the shop, using the brand they prefer. That way if there is an issue with them the shop should stand behind what they sell. If you are doing it yourself, Yukon and Dana are the two brands I would trust.
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Old 11-27-2019, 11:56 AM   #9
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I have 4.56 on my D30 with 35's. Perfect to me. I decided not to lock the front because of all the stuff I read about my toothpick axle. Hindsight I would put a Tru Trac up front and selectable rear. I know my D30 is a weak point and don't drive it like I'm on tons.

For what your saying, 33's I would go 4.10 with tru trac up front and selectable lock rear (or selectable both if money doesnt stop you).
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Old 11-30-2019, 12:35 PM   #10
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Regearing and lockers on a D30 is money down the drain. Use the money and buy an aftermarket D44. Look around on CL. I sold my PR44 for a great price with only 10K miles on it. Guy that bought it lives in Minnesota and we shipped it from Arizona.


Yall realize that the standard factory D30 and D44 share the same axle tubes and Cs. Center forging along with ring and pinion size are the differences.
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Old 11-30-2019, 12:39 PM   #11
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Yall realize that the standard factory D30 and D44 share the same axle tubes and Cs. Center forging along with ring and pinion size are the differences.
It's the R&P difference, plus I would go aftermarket to beef up the tube wall thickness and C's.
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Old 11-30-2019, 12:52 PM   #12
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Going from 3:21's in my 75th JKU I will be re-gearing with 4:56 and running 315's with this Detroit Locker 912A585 Detroit Trutrac by Eaton Performance Limited Slip up front. I hope this will do well???????
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Old 11-30-2019, 02:36 PM   #13
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Hello,

Which lockers should I buy - have a Sport S automatic (with 3.21 gears). Tired of constant auto shifting on hills. Might upgrade to 33s someday (no lift now). Thinking 4.56? Any brand better than another?

WRT lockers, I see "27 spline" "30 spline" etc. Which do I use for a stock Sport S with D30F and D44R?

Thank you in advance.
"Tired of constant auto shifting on hills." Even with an automatic and 4.56 gears, manually select gears on hills, up and down.
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Old 12-03-2019, 10:30 PM   #14
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Going from 3:21's in my 75th JKU I will be re-gearing with 4:56 and running 315's with this Detroit Locker 912A585 Detroit Trutrac by Eaton Performance Limited Slip up front. I hope this will do well???????


Does excellent.
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Old 12-04-2019, 06:03 AM   #15
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Like you, I have a Sport S that started with 3.21s. You can see the details of mine so far, in my sig line below. This far, for my relatively mild wheeling and rock crawling, I'm very happy with the LSDs front and rear, though the Aussie in the front can get rather aggravating when negotiating tight turns on pavement.

Were I going to stay with 33s, I'd have done 4.10s, but I went with 4.56s since my plan involves 35s.
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Old 12-04-2019, 08:45 AM   #16
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Does excellent.
Thank you!!!!
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Old 12-04-2019, 08:46 AM   #17
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Like you, I have a Sport S that started with 3.21s. You can see the details of mine so far, in my sig line below. This far, for my relatively mild wheeling and rock crawling, I'm very happy with the LSDs front and rear, though the Aussie in the front can get rather aggravating when negotiating tight turns on pavement.

Were I going to stay with 33s, I'd have done 4.10s, but I went with 4.56s since my plan involves 35s.
4:56's is the way, only 150 revs over 4:10's and you wont need to upgrade unless you go with 37s.
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Old 12-04-2019, 12:18 PM   #18
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I also have a Sport.

I had a Lockright with 4.56 gears on 35's and wheel in rock. I would seriously reconsider an auto locker in a D30. A truetrac is slightly better but if you insist on locking a D30, get a selectable locker.

I destroyed my D30 on an obstacle. Took out the carrier bearings, both axles and the locker.

I would just save my pennies for an upgraded axle if you plan on doing any serious wheeling. You can get a full aftermarket D44 with gears, locker and chromolly axle shafts for under $4K.
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Old 12-05-2019, 08:53 AM   #19
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4:56's is the way, only 150 revs over 4:10's and you wont need to upgrade unless you go with 37s.

Not an entirely true statement. 4.56 can be perfect with 37's (rolling hills of N. Alabama). I have 2 jeeps set-up like this and one on 35's with 4.10.

Use the calculator at Grimm Jeeper and make sure you are using the ACTUAL tire size and not what is printed on the sidewall so you can see speeds/RPM combos for each gear ratio.
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Old 12-09-2019, 05:01 PM   #20
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I just teraflexed the heck out of my JKUS. I sleeved and gusseted the front axle and re-geared to 4.10 f/r and put a trutrac in the rear. The 33"s look a little small and think I might want to run 35"s when these are shot. I'm just not sure the D30 can handle it no matter how much I beefed it up. Also thought about putting selectable up front but again, D30.

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