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Unread 05-03-2008, 05:54 AM   #1
Soft 8
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JK Limited Slip rear VS Electronic Locking Rear - Difference?

I am "building" a JK on www.jeep.com and was wondering what the difference was between the two. My GF's Jk has the Limited slip and it works great but What is the Electronic locking rear? Anyone have any infomormation on it? Is it really worth the extra money?

Quote:
Trac-LokŪ Limited Slip Rear Differential $295

Tru-LokŪ Electronic Locking Rear Differential $750


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Unread 05-03-2008, 06:26 AM   #2
68redcat
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locker will put 100% of all power to the rear 2 tires, limited slip will 100% of the power to one tire and slip from the left tire back to the right tire but at NO TIME WILL BOTH TIRES GET POWER AT THE SAME TIME.
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Unread 05-03-2008, 08:01 AM   #3
igofshn
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Quote:
NO TIME WILL BOTH TIRES GET POWER AT THE SAME TIME.
On dry pavement they do.
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Unread 05-03-2008, 10:22 AM   #4
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When adding the rear Tru-Lok to an X you also must add the Sway bar disconnect (Invoice price for the pair is aprox $1200)


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Unread 05-03-2008, 11:03 AM   #5
That1guy
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The locking rear works alot better than the limited slip.
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Unread 11-20-2008, 03:39 PM   #6
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Let's take the question from a different angle. What problem is each trying to solve? Or in what situations does one excel verus another?
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Unread 11-20-2008, 04:20 PM   #7
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Okay.......(I'm about to write a short book on differentials here)

When you drive a car around a corner on dry pavement the left and right wheels spin at different rates of speed. In order to accomplish this the axle must be able to "differentiate" between the right in left.

OPEN

In a normal car this is done with an "open" differential. The basic effect here is that the tires can openly spin at different speeds. When you apply throttle all the power will go to the wheel with the LEAST traction. This is why you see cars stuck in the snow and only one wheel is spinning. On perfectly flat ground in a perfect straight line an open differential will even spin both tires. Add even the slightest variation to traction or road surface and only the wheel with the least grip gets the power. This is all done with "spider" gears inside of the differential carrier.

LIMITED SLIP

A "limited slip" differential is builds on the open differential by adding a friction device in the differential. Mostly this is clutches and sometimes additional gears (torsion). These simply take more friction applied to them to cause the wheels to spin at different speeds. (it limits the amount of "slip" from one wheel to the other). So in normal dry pavement driving they will act just like an open differential to a point. On a slick or imperfect surface both wheels will spin up to a point. At some point (depending on how tight the clutches are) friction takes over and the wheel with the LEAST traction will spin. These are great for race cars or trucks doing towing. But on a 4x4 wheel one wheel may have no traction at all, that wheel will get the power, which will NOT move you forward.

The "Brake lock differential" simply applies brake pressure to the wheel with the least grip to cause it to have friction which in turn helps send power to the opposite wheel. This is good, but not great Since a wheel off the ground can't slow down anymore to transfer the power. (plus you are braking while trying to move forward).

LOCKERS

There are 2 main type of lockers. "Selectable" and "full time". A "full time" locker is a ratcheting mecahnical linkage that connects the left and right wheel. They will provide 100% power to BOTH wheels even with one off the ground. They are designed to "open" and freewheel one wheel when going around a corner on the street ONLY when you are not on the throttle. You apply pressure to the pinion and they will lock up. Even when off the throttle the power is going to the wheel with the most grip. These are tricky to drive on the street because they don't offer true differentiation on the street especially on slick roads where there is not enough friction to cause them to unlock. So in a corner both wheels are spinning the same speed. This must force one wheel to break traction and spin. So this wheel no longer has the lateral traction in the corner, plus both rear wheels are pushing the vehicle in a forward motion even though you are trying to turn. (squirly on slick surfaces).

"Selectable lockers" are what is in the JK. This is basicly a full "open" differential for street use and a fully locked "Spool" for the trail. (a full solid lock of both axles no matter what pressure is applied to them). "Open" differentials are the easiest to drive on the street. Even a tight "lsd" can cause stability loss on a slick surface.

A full "spool" (engaged selectable locker) is the best off road because it makes both wheels spin the same speed even if one is up in the air.


SPOOL


A full solid mechanical lock of the left and right axle that can't be unlocked or open ever.

LINCOLN LOCKER

A poor mans spool made by taking a "Lincoln electric" welder and welding all of the spider gears inside an open differential to create a fully locked differential.

Spools in any form (selectable locked, lincoln locker etc) are VERY hard on axle shafts and other drivetrain components when opperated on high traction surfaces.



Hope that helps.
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Unread 11-20-2008, 04:31 PM   #8
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Get a rubicon and then you have front and rear locking differentials and electronic sway bar disconnects.
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Unread 11-20-2008, 04:57 PM   #9
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Quote:
Originally Posted by Soft 8 View Post
I am "building" a JK on www.jeep.com and was wondering what the difference was between the two. My GF's Jk has the Limited slip and it works great but What is the Electronic locking rear? Anyone have any infomormation on it? Is it really worth the extra money?
I had a limited slip rear on my TJ. It was worthless. I got better traction assist by pulling my emergency brake on about 3/4 to stop the spinning wheel than the LS ever did. I switched to a Detroit Locker for the rear. It had rude behavior on road but was a gem off road. I have factory lockers on my Rubicon JK and the vehicle is almost unstoppable. If the tires hold traction I will go.
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Unread 11-20-2008, 05:52 PM   #10
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Limited slip will also lock up on slippery roads, I did a complete 180 in my Power Wagon in those conditions and after plowing snow with them, there is no doubt that occurs. If you are on a slight grade, they will go sideways on you as well. Even my newer Ram does this, I need to be careful backing into my barn since the limited slip will torque the vehicle sideways and into the wall if I am not careful.

That is exactly why I wanted lockers on this Jeep and not limited slip. The traction control does work well.
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Unread 11-20-2008, 10:39 PM   #11
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Excellent explanation from Xtremjeepn. I wish I had that when I was trying to make the same decision, or had read the owners manual prior to purchase (not realistic, I know). I was thinking of the full locker but since it was only available in combination with the unlocking sway bar, I got the limited slip. In hindsight I would not have bothered with either since I don't do any extreme off-roading.

The electronic traction control is amazing on the JK for on-road use, much better than any previous limited slip vehicle I have had, and the traction control basically has limited slip built in already. Also, limited slip has a limited life expectancy for the limited slip part. Do an internet search - I think they don't last more than 50,000 mi and then are effectively open differentials.

If you want the primarily off-road advantages of the full locker, then you'll have to spend the dough. I'd skip the LSD otherwise.

Hope this helps.
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Unread 11-21-2008, 07:00 AM   #12
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agreed. clear, concise, to the point. and more importantly, not full of it. then again, the newer wranglers have the bld, and that makes up for quite a bit.
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good grief, just buy the Rubicon.
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Unread 11-21-2008, 07:12 AM   #13
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Quote:
Originally Posted by Xtremjeepn View Post
... The "Brake lock differential" simply applies brake pressure to the wheel with the least grip to cause it to have friction which in turn helps send power to the opposite wheel. This is good, but not great Since a wheel off the ground can't slow down anymore to transfer the power. (plus you are braking while trying to move forward)...
Nice explaination Cole, but I thnk you should give Jeep's BLD a little more credit. Here is a good description of what it is and what it does and does not do:

http://blog.chryslerllc.com/blog.do?p=entry&id=270
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Unread 11-21-2008, 08:40 AM   #14
That1guy
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You guys know this thread is almost 7 months old right?
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Unread 11-21-2008, 09:52 AM   #15
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Originally Posted by That1guy View Post
You guys know this thread is almost 7 months old right?
Still good info.
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