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    Default differential lock

    what is meant by differential lock does any body clearify it

    thanks
    -

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    Differential locks , when engaged properly guarantee equal wheel speed on all 4 wheels. Spinning wheels are prevented.
    Heavy duty off-road situations ask for three (center differential & front and rear axle differentials) manually and independently lockable differentials. Dog clutches provide the lock up.
    I don,t believe in taking right decisions, i take decisions and make them right !

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    Most Defenders if not all come with factory fitted Diff locks. Even some Toyotas 4x4s come with factory fitted Diff locks.

    Also many after market Diff locks are available for Lockrite, Detroit Lockers, ARB and other companies. ARB Diff locks are considered to be one of the best after market locks.

    By the way i am searching for a 1990-94 Prado or 1995/97 model Land Crusier with Diff locks. IF anyone is selling one then please do contact me.

    Regards
    Sajid
    Pakwatan Explorer

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    Its rather complicated, but lets give it a go;

    Diff locks in 4X4s are: Central, to make sure equal torque distribution to front and rear wheels. Additonally in some vehicles there are separate front and rear diff locks to make sure that equal torque is sent to right and left wheels. Theoratically one would have the most traction with all diff locks engaged, however lots of other things come into play (to avoid wheel spinning/ improving traction) including the tyres and suspension (tyre contact/grip to any surface depends on your suspension, be it off-road or onroad vehicle).

    Limitations of full diff locks is that it can be used on only slippery surfaces as wheel speed on all 4 tyres is same. Which mean that transmission is under lots of stress when turning etc because wheels are covering different distances in turns (ouside more that inside tyres). You can actually snap your transmission on grippy surface by constantly turning with full diff locks engaged.

    Diff locks are meant to help in avoiding the wheel spins, so you can keep moving forwards (or backwards). Theoretically in most 4X4s, when on steep uphill slope with two wheels on ice/very slippery surface, the vehicle would not move forward, but rather the wheels on slippery surface would keep spinning. So in real term these vehicles are not 4 wheel drive. However if you have full locks on than this could be avoided, as tyres on left and right side can only turn at one speed, so no power is wasted on spinning.

    Manufacturers use various other things to avoid wheel spin as well, like Limited slip differential, torsen diff locks, traction control systems etc.

    Most Proper 4X4s would have central diff lock. Soft roaders mostly wouldn't. Very few 4X4s would offer full diff locks even as an option. G-Wagens have offered them standard from beginning (apart for G500 for some model years), Some models of Jeeps and I beleive Hummer H1 also had them.

    As far as I know Defenders and even other land rovers/ range rovers would mostly just have central diff locks. But they mostly can make up for that from there excellent suspension.

    Landcruisers series 80 had front and rear diff locks only as an option. In Series 100 only rear diff locks were available. Not sure about series 200. I think its similar for old and new Prados.

    As mentioned in other replies, you can also get some after market diff locks, including full diff locks.

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    Excellent knowledge sharing guys. I am Impressed
    Keep a cool head and wear seatbelts!

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    @spectra, Its a jeep thing, Lots of people does not understand.......
    -

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    4x4 's to the rescue


    well
    guys

    i just came up with a question





    what about 4x4 cars
    like evolution, rs4 etc etc
    (1)Austin of England, a35, 1958, 850cc,,, (2) Mercedes benz , w202, C - 180 ,,, (3) 2003 HONDA CITY,,,, (4) Triumph TRW 500cc, 1952,,,,

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    @Wasif

    Am not an expert, but cars do not have diff locks, even if they are all wheel drive / 4 wheel drive. As mentioned before, there are limitations of differential locks (even just central differential locks) on grippy surfaces such as road (where cars are used all the time). They do however have limited slip differentials to reduce individual wheel spins etc as well the various kinds of traction control systems or anti skid systems.

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    Nice info
    -It is always Man behind the Machine.

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    In addition to factory installed diff locks, there are several aftermarket options to add a differential lock to front and rear axles. ARB Air Locker, Detroit Locker, Eaton Locker are probably the best known. Recently we saw some newcomers like the OX Locker which seems like a copy of a long know German Schwarz locker to me.
    I don,t believe in taking right decisions, i take decisions and make them right !

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    nn

    The HMMV or the Hummer H1 has (or had) Torsen differentials. That is, they bias torque to the wheel that has more traction. One caveat of this design is that it can only multiply the torque sustainable by the wheel which is slipping. That is to say, that it multiplies the minimum sustainable torque on the axle and sends it to the one that's spinning slower.

    At the start, civilian drivers didn't know how to use the diff as it would imitate an open diff. It later turned out that you have to ride the brake with your left foot to increase the minimum torque sustained by the axle, thus you can bias more torque to the slipping wheel.

    *Its a bit easier to understand than it is to explain*
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    P.S. On road cars such as Audis (with longitudinally mounted engines) have Torsen diffs. Others have a clutch pack / viscous coupling that engages if one axle (front or rear) loses traction. In the Evo and WRX, there's a proper LSD (plate-type) in the center. In a Skyline, it's a viscous coupling.
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    @ Sami

    Thanks, I did mention, am not an expert. Also did mention regarding the torsen diffs.

    And you do have to be moving somewhat for the torsen diff to be of some benifit, as in if you are stuck still than torsen diff would do nothing (where as full diff locks would). Thats why momentum is of great importance in off-roading.

    In the end this may all be an academic discussion, as experience, traction and several other things would also have similar importance in any given situation while off-roading.

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    nn

    Very rightly said. In a lot of off road situations, only momentum can get you out. And a locking diff will make no improvement to your progress if you do not know how to use them properly. They only improve the utilisation of available traction, they don't increase it.

    As a side note, I've experienced what's known as a "crow's-hop" when I've (very occasionally) driven my 3-dr Pajero in 4WD on a metalled road surface. That's because it hasn't got a differential in the front or at the center, and an LSD at the rear.
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    @experts
    I heard differential locks breaks if you drive on road? you have to disengage when on roads, is it right?
    Thanks to ALLAH for everything | Love what you have!

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    @s55

    Diff locks when engaged make the tyre/wheels rotation equal for front and back or even left and right side depending on what diff locks are engaged.

    So unless you drive just straight ahead continuously (or you disengage the front wheel hubs manually) due to different rotations in front and back wheels and also inside vs outside wheel while turning will put enough strain to break something in the differentials/ cogs or somewhere in drive line. Having said that you have to have same size tyres allround with equal wear and same pressure to make sure nothing breaks even if going straight.


    @ Sami

    Am not aware of the crow's-hop term. What does it actually imply, the kick back jerk from steering wheel and the jumpy inside wheel when turning on grippy surface?? And why would it happen in your Pajero's case without the differentials?

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    @all
    nice info really interesting,
    @sami_vodoo
    do u have msn?

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    nn

    I've got a Pajero 3-dr 1st gen with manual hub locks. I think that on those models you do not have a front differential. When you lock the hubs, the front wheels turn at the same speed.

    Since the vehicle is part-time 4WD, you've got a silent chain drive in the transfer case that transfers drive from the gearbox output towards the front wheel when you want 4WD. There too, there isn't a differential. Thus when driving, the front-to-rear axle speeds are the same. And the front wheels turn at the same speed.

    The 1st gen Pajero came with auto-locking front hubs, with permanently engaged front hubs, and auto-locking front hubs.

    As for the "crow-hopping", the first thing you notice is that the steering wants to straighten itself out as soon as you touch the accelerator. The second thing is that on a turn, it jumps (or hops - hence the term) alternatively from the front and the back. And you can even see tire marks on the road (a bit like Morse Code ).

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    Sami

    I had one of those (Pajero) for over 6 years. It had auto locking front wheel hubs. Not sure but there should have been a front differential, or something to allow different tyre speeds for turning. Obviously being part time 4 wheel drive, the front wheels got their drive from the transfer case as you said.

    My explanation would be that because of grip on asphalt, if you have equal speeds to front and rear drive shaft you would get your crow's hop anyway even if front diffs are not locked, because your rotation speed of both front wheels would still be different to rear one while turning.

    The LSD probably gave minimal benefit in off-roading. Atleast that was my personal experience or could be in-experience at the time!


    differential lock -870502

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    nn

    About the LSD you're quite right - it's not the best thing in the world, but it does help out quite a bit. Let's say you can climb up a 15° grade with one rear wheel hanging in the air in 2WD. Then again, mine's been in the family since new in 1990 and it was never abused. Maybe the one in yours was a bit loose? And was your's a 5-dr? That might explain its looseness as well...

    About the crow-hop, you're right as well, because the Ackermann geometry built into the front allows the wheels to turn more or less around the same point, but the distance from that point is different for the front and rear axle, thus the difference in speeds required. When I get back home, I'll jack one side up and try to see if there's a diff in there somewhere...

    Cheers!
    Sami
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