06 LJ Rubi on 36” IROK : preventive solution - Rubicon Owners Forum
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post #1 of 13 (permalink) Old 01-02-2020, 04:01 AM Thread Starter
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06 LJ Rubi on 36” IROK : preventive solution

Hi There i have an 2006 LJ with 4.88 R&P and rear alloy usa HD shafts and front RCV axles.

Jeep has been off roaded in sand dunes and now mostly rocks and snow.
37 k miles.
Breakages to date: 1 R&P , Front axles the U joints....

Is the weakness in the rear end locker mainly from the stock LSD ?

When it breaks it will probably mess up the R&P right ?
Should i upgrade to an ARB in the rear ?

Will this affect the on road stability ad i drive my Jeep to the trails.

Pls advise

Jay

2006 Jeep Rubicon Unlimited - AEV Kit, Nth Tummy Tuck, 3" FT,Bumpers,JKS....
1996 Land Rover Discovey on 36.5" IROKS(30 splines, longfields CV's,Toy 8" Diffs, ARBs,M8274-50,custom bumpers...)
1983 Range Rover Stock
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post #2 of 13 (permalink) Old 01-02-2020, 08:46 AM
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Sounds like you have a solid handle on the common weaknesses. Whenever something breaks, its a good practice to inspect everything since one failure often causes others. An ARB is a great upgrade and is much stronger than the OEM unit. Leaving the ARB unlocked will make the jeep handle great on the road and when locked, is basically a spool offroad.
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post #3 of 13 (permalink) Old 01-02-2020, 09:08 AM
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you might consider a 60 if the rear lets go. Not that much more money, especially at this age with the jeeps. IMHO.

Going through the rear end of the LJ now, and by the time brakes and everything else, plus labor. I should of gone with plan 1, but plan 3 took over.
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post #4 of 13 (permalink) Old 01-02-2020, 10:05 AM Thread Starter
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Originally Posted by Mouse View Post
Sounds like you have a solid handle on the common weaknesses. Whenever something breaks, its a good practice to inspect everything since one failure often causes others. An ARB is a great upgrade and is much stronger than the OEM unit. Leaving the ARB unlocked will make the jeep handle great on the road and when locked, is basically a spool offroad.
Usually with the LJ rear end would the LSD break first ?

2006 Jeep Rubicon Unlimited - AEV Kit, Nth Tummy Tuck, 3" FT,Bumpers,JKS....
1996 Land Rover Discovey on 36.5" IROKS(30 splines, longfields CV's,Toy 8" Diffs, ARBs,M8274-50,custom bumpers...)
1983 Range Rover Stock
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post #5 of 13 (permalink) Old 01-03-2020, 09:40 AM
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Originally Posted by jayfrem View Post
Usually with the LJ rear end would the LSD break first ?
The rear axle takes most of the abuse when rock crawling so generally it's the first one to break. I broke the spider gears in my stock rear diff but the R&P was okay as I recall, I do think the LSD makes the diff more breakage prone. A popular upgrade is to replace the rear diff with either a Rubicon front diff or an ARB, E locker or whatever floats your boat.

As inline6 mentioned the ultimate 'fix' is to upgrade to a D60 (which I did.)
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post #6 of 13 (permalink) Old 01-03-2020, 06:13 PM Thread Starter
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Originally Posted by jayfrem View Post
Usually with the LJ rear end would the LSD break first ?
The rear axle takes most of the abuse when rock crawling so generally it's the first one to break. I broke the spider gears in my stock rear diff but the R&P was okay as I recall, I do think the LSD makes the diff more breakage prone. A popular upgrade is to replace the rear diff with either a Rubicon front diff or an ARB, E locker or whatever floats your boat.

As inline6 mentioned the ultimate 'fix' is to upgrade to a D60 (which I did.)
Wouldn't t a Dynatrac housing be a better option if i am staying with 36” ...

D60 lowers ground clearance as diff housing is larger.

Some suggested to keep the rear lockec off pavement to bypass LSD at all times.

2006 Jeep Rubicon Unlimited - AEV Kit, Nth Tummy Tuck, 3" FT,Bumpers,JKS....
1996 Land Rover Discovey on 36.5" IROKS(30 splines, longfields CV's,Toy 8" Diffs, ARBs,M8274-50,custom bumpers...)
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post #7 of 13 (permalink) Old 01-04-2020, 09:23 AM
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Limited slip is always 'engaged' - you can't turn it off. My Dana Rock Jock 60 is a high pinion model and with my 37" tires and tummy tuck I have great clearance and the drive shaft is mostly out of harm's way. With the D60 install I had the shop four link it so I could get rid of the track bar - makes a huge difference with rear articulation.

As far as a Dynatrack housing, I see no advantage with changing the shell of the rear axle - you are still restricted with the smaller diff. I had an entire D44 G2 rear axle installed at Moab Outpost a few years ago and on a very steep climb in a rock notch the axle tube pulled out of the cast iron diff housing. It pulled out enough to where there weren't many axle shaft splines engaged and the engaged splines spun right off. That was a very tricky place to have three wheel drive.
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post #8 of 13 (permalink) Old 01-04-2020, 09:33 AM
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Originally Posted by jayfrem View Post
Wouldn't t a Dynatrac housing be a better option if i am staying with 36” ...

D60 lowers ground clearance as diff housing is larger.

Some suggested to keep the rear lockec off pavement to bypass LSD at all times.

These are all good questions that lead down the long road of possible axle upgrades. To help you find the right combination of reliability versus cost, we need to know what kind of wheeling you plan to do, what size of tires you think you'll run, and whether you plan to increase HP. Like John, my TJ runs a high pinion Currie RJ 60 in the rear, but for my jeep I've reached the limits of it's strength and it is a reliability issue (running 40 inch tires will do that). My opinion is that a high pinion 60 for a rear axle is for 37 inch tires and lower. The limit is primarily ring and pinion strength, although in my case I've wiped out wheel studs (since upgraded to 5/8") and twisted axle splines with the stock 4.0L engine.

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post #9 of 13 (permalink) Old 01-06-2020, 10:10 PM
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I was running 36” Iroks on my LJ when I sheared off the rear pinion shaft. That gave me a reason to finally move up to 5:13’s.

Move forward two years and now one of the spider gears in the limited slip is missing about 8 teeth.

I agree with what others have said about locking the rear axle at the trail head and leaving it locked all day. That way the limited slip part is out of play. Pretty sure wheel spin without the locker on us what kills the rear lockers when on 33” or bigger tires.

I’m going with Dana 60’s soon since I’ve limped off the trail two of the last five wheeling trips.

For you I am afraid it is when and not if the rear is going to let go.
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post #10 of 13 (permalink) Old 01-07-2020, 09:30 AM
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.....I’m going with Dana 60’s soon since I’ve limped off the trail two of the last five wheeling trips. For you I am afraid it is when and not if the rear is going to let go.
I was always careful with the throttle and never let the front bounce more than one time (even that was a rare occurrence.) You are right, a rear D44 and >=35" tires will indeed break at some point in time assuming rock crawling is involved and not just running forest trails.

The Currie RockJock high pinion D60 is a very, very good axle for the money and it can be configured with the TJ/LJ wheel stud pattern and the same side to side width. Since I had expensive beadlock rims I wanted to keep the same bolt pattern on the D60.
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