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  1. #1
    TerryMason's Avatar
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    What is a locker and how does it work?

    I remember years ago, taking my Jeep offroad and being shocked when one of my rear tires lost traction and began spinning - the other rear tire just sat there doing nothing! I double checked that I was in 4WD, but the tire in the air kept spinning while the one on the ground just sat there... mocking me.


    Open Differentials
    To understand the need for a locker, you first have to understand the way the majority of Jeeps come from the factory - with an "open differential" (sometimes called a factory differential), or as it's commonly called, and open diff.

    Photo of a Dana 35 with an open differential:
    What is a locker and how does it work?-dana-35-open-diff.jpg

    Without getting overly technical, the engine likes to split the torque sent to the wheels in a 50/50 ratio (50% of torque to the left, and 50% to the right). If the left wheel is up in the air the engine sees a reduced resistance and will reduce the amount of torque sent to the axle. Since torque is split 50/50, both the left and the right wheels get a fraction of the torque they need to move the vehicle forward, and you stay stuck.



    Lockers
    A locker does as the name implies - it mechanically locks the left and the right wheel together. They will spin at the same speed. This is great for offroad because if one wheel is up in the air then the other will still spin. The problem comes when you want to drive your Jeep on the street.

    Photo of a Dana 35 with an mechanical locker installed:
    What is a locker and how does it work?-dana-35-locker.jpg

    When you make a turn the inner wheel travels a shorter distance than the outer wheel, and during the turn the spin at different speeds, as you can see in the picture below:

    What is a locker and how does it work?-how-differentials-work.jpg

    If you have mechanically locked the wheels together, then you'll have a hard time turning since both tires will attempt to travel the same amount of distance, causing some strange handling problems. This is why there are several types of lockers that allow you to manually engage and disengage them.

  2. #2
    bugleboy's Avatar
    bugleboy is offline Senior Member
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    awesome info :) i might need something like this

  3. #3
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    Re: What is a locker and how does it work?

    Awesome info, Terry, thanks!

    That being said, I have a 2005 TJ (an new to the Wrangler), fully stock drivetrain. I do very little off-roading currently. However, I do want better traction during the winter months (can get interesting up here in Buffalo).

    I have been looking at lockers -- what a selection! Is a Detroit Tru-Track a good choice?

  4. #4
    TrailRatedRN's Avatar
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    I want air lockers. ARB is what they all yell is premier. Expensive. But I love the idea of freedom to unlock at will and have onboard air. I'd like to install myself some day, but I'm scared of the differential. I just picture me taking the cover off to find a pool of metal shavings after I've done the job.

    Ps I love the color used for marking. My alma mater is blue and gold

  5. #5
    69jeepcj's Avatar
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    Re: What is a locker and how does it work?

    Locers will disengage when you let off of the throttle, and engage when the throttle is applied. In my opinion, a jeep that is driven mostly on road should get a selectable locker such as the air locker. I have wrecked two jeeps with lockers on snowy roads in 2wd. They work great when engaged in 4wd on slick roads because the front is pulling as the back is pushing. When in 2wd on slick roads, it is a nightmare. Both back wheels are turning at the same power and leaves you sliding all over the road with any throttle change. I would rather drive a open dif in 2wd on slick roads any day over a locked rear in 2wd on slick roads. A selectable locker will allow you to turn them on and off as needed. Just a caution with lockers and snowy roads in 2wd.

  6. #6
    bugleboy's Avatar
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    my jeep is 2wd would this be a good idea for offroad or a waste of money? ive flexed on a few dirt hills and such before and when that back tire doesent have much weight on it it gets a spinnin and the wheel fully on the ground goes nowhere without some gas, also im one of those one wheel wonder burnout jeepers lol mine is quick and i live to race it aginst ricers in their little hondas (i win 95% of the time) would an air locker give me that extra boost if i locked my rear and let me do a burnout with both the wheels?

  7. #7
    69jeepcj's Avatar
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    Re: What is a locker and how does it work?

    The Detroit true-trac is not a true locker, I don't know the correct term but it is a limited slip or posi unit. The clutches in it are much tighter than in other similar units and is as close to a true locker as you can get.. They are highly recomended for front axles due to the clutches allowing slippage in the front tire making tight turns much esier with out the plowing effect you get from a true locker. I have a detroit locker in my rear and a true trac in the front of my jeep. Im my opinion a true trac in the front or rear would be a great choice for the street driven weekend wheeler jeep.

  8. #8
    69jeepcj's Avatar
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    Re: What is a locker and how does it work?

    Buggle boy, a automatic locker would help you offroad like night and day even in 2wd, on sick streets use caution though. As for the burnouts, you probably wouldnt be able to burn out any more due to the increased traction at BOTH tires. If you have a v8 that may be a dif story though.
    When I first went to lockers, I had to find new trails because the ones I was running were not fun anymore. I could drive most of the trail in 2wd.

  9. #9
    bugleboy's Avatar
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    Quote Originally Posted by 69jeepcj
    Buggle boy, a automatic locker would help you offroad like night and day even in 2wd, on sick streets use caution though. As for the burnouts, you probably wouldnt be able to burn out any more due to the increased traction at BOTH tires. If you have a v8 that may be a dif story though.
    When I first went to lockers, I had to find new trails because the ones I was running were not fun anymore. I could drive most of the trail in 2wd.
    okay thanks :) im definatly shopping around, and my old 4.0L probibly shouldent be breaking both tires loose anyway lol but i need something for that slippy axle

  10. #10
    TrailRatedRN's Avatar
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    Quote Originally Posted by 69jeepcj
    When I first went to lockers, I had to find new trails because the ones I was running were not fun anymore. I could drive most of the trail in 2wd.
    Lmfao. Sweet.

    My jeep is also my dd, that's why I like the air locker. One can just unlock at will. I thought about cable, but I hear the cable lockers have more trouble with line breakage.

  11. #11
    bugleboy's Avatar
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    mines my dd too air locker sounds good

  12. #12
    69jeepcj's Avatar
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    Re: What is a locker and how does it work?

    I have read about problems with the cable operated lockers too! I don't think they have been around to long so maybe they have some bugs to work out. Air lockers are expensive but the best option.

  13. #13
    bugleboy's Avatar
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    you mean like the ones with the knob to engage? or like switch operated? or both

  14. #14
    TerryMason's Avatar
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    Re: What is a locker and how does it work?

    A cable locker (namely the OX locker) is engaged by a cable that is routed through a special diff cover and into the cabin. You push or pull the cable to engage or disengage the locker (similar to an old lawn mower cable or a bike hand brake).

    An air locker, like an ARB is powered by an external air compressor, and engages / disengages the locker by air pressure (like an air tool).


    Air lockers vs cable lockers if kind of like Ford vs Chevy. You'll generally hear that when an air locker breaks (break in the air line) it's an easier trailside fix than when a cable locker breaks (the cable gets crimped / freezes). I believe that an air locker generally costs more, but at the same time you'll be able to air up with the compressor.

  15. #15
    bugleboy's Avatar
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    hmm... id probibly go with the cable because it costs a little less and i could probibly put the knob where my 4wd shifter would go if i had one

    What is a locker and how does it work?-image-132602046.jpg

  16. #16
    808CJ7's Avatar
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    As long as it doesn't interfere with the hula dancer ha ha ha

  17. #17
    bugleboy's Avatar
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    haha yeah if i had 4wd there would be nowhere to put her at all, the windshield is to darn steep and theres not enough dash space

  18. #18
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    Re: What is a locker and how does it work?

    the locker that is installed in the photo above...what brand is it? Are they reliable and/or worth a darn?

  19. #19
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    Re: What is a locker and how does it work?

    I have arb lockers if there is no air getting to the diferitial would that cause the axles not to turn at all

  20. #20
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    Re: What is a locker and how does it work?

    Terry Mason didn't include the third type of locker, which is electric. I have electric lockers in my jkur, and ARB's in my old school Jeep. I prefer electric lockers for ease of install but, ARB's are probably a more stout of a locker.

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