Centre diff locks.

Submitted: Friday, Jan 13, 2006 at 20:30
ThreadID: 29672 Views:2124 Replies:2 FollowUps:6
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Hi all.
Have found lately that the centre diff lock on the landy has been more of a hinderance than help. To access job site this week ,have had to pull through about a km of really soft sand( I mean soft) half way up wheels but hard ground underneath. Normal 4wd gets me there . but if i engage diff lock it wants to jump and skip around. I guess this is because two wheels are locked on one side.If one side of track was soft and the other hard the diff lock would help out??.Anyone experienced the same issue???

Regards Axle.
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Reply By: desert - Friday, Jan 13, 2006 at 20:39

Friday, Jan 13, 2006 at 20:39
I would suggest that the jumping around you are experiencing is the act of the car gaining bite or traction. Without the lock on, you are merely applying heaps of wheel spin (most likely all to the front wheels), risk damaging the transfer case and busting the third diff centre. Next time, let your tyres down to a sand pressure of around 16 psi and walk through! Easy.
AnswerID: 148418

Follow Up By: Ken - Friday, Jan 13, 2006 at 22:20

Friday, Jan 13, 2006 at 22:20
I agree with this. The centre diff lock is simply that, it does not lock the axle diffs as many people seem to think. Without the centre diff locked the power will always go to the wheels with the least grip, just like the front and rear diffs. Spinning the wheels on either axle give the diff mechanicals a terrible time as the sun gears, which have no bearings, turn furiously in the diff carrier. The centre diff is no more robust and unlocked all the torque goes thu one side of the diff centre and will certainly do serious and expensive damage if you persist.
As you say the "jumping" is very likely due to varying front and rear traction as both ends of the vehicle are now driving. Without and AXLE diff lock you will still experience wheelspin from wheels on one side or the other in some conditions and the centre diff lock can never control this.

FollowupID: 401687

Reply By: Member - Willie , Epping .Syd. - Saturday, Jan 14, 2006 at 14:32

Saturday, Jan 14, 2006 at 14:32
Hi Ken ,

I am still confused . I have front and rear diff locks on my 100 TD . In what situations should I use the centre diff lock ?? Should it only be used when either the back or front has traction and the other does not or should I use it in other situations .

I am a mechanical idiot , sorry .

Thanks ,

Willie .
AnswerID: 148524

Follow Up By: Axle - Saturday, Jan 14, 2006 at 14:57

Saturday, Jan 14, 2006 at 14:57
Its got me going a bit now. What i was saying that with centre difflock engaged I had less traction than in normal 4wd. If what Ken is saying is right which I have no doubt he is, than a 4wd with no difflock what so ever is going to be a very vunerable machine mechanically in rough going.

FollowupID: 401775

Follow Up By: Member - Davoe (Widgiemooltha) - Saturday, Jan 14, 2006 at 15:01

Saturday, Jan 14, 2006 at 15:01
I have never owned a constant 4wd but AFAIK the constant 4wd gives you better grip on wet roads and gravel roads. You need to engage the centre diff lock in low traction situations. (EG if you saw me jump out and click the hubs in and put it in 4H then that is when you would engage the centre lock). For additional traction at low speeds in really muddy/sand/ steep/loose/all of the above you would additionally turn on the front and rear lockers but only for the duration of the extreme conditions
Hope this helps
FollowupID: 401776

Follow Up By: madlee - Saturday, Jan 14, 2006 at 17:24

Saturday, Jan 14, 2006 at 17:24
You engage the centre diff lock in the same situation as you would engage 4wd in a standard 4wd.you use front and rear diff locks to go where a standard 4wd can't.
FollowupID: 401784

Follow Up By: Ken - Sunday, Jan 15, 2006 at 18:26

Sunday, Jan 15, 2006 at 18:26
Willie, the responses are all good info and you are not an idiot for asking !
The front an rear axle diff locks provide awesome capability for your cruiser when used correctly. Steering will be greatly effected so give it a try somewhere where this doesn't matter. The diff are designed to let the inner and outer wheels rotate at different rates when turning. This is a great thing for turning but unless the traction is the same on each wheel the clever little gears inside the diff send the power to the wheel with the least grip, generally causing it to spin and hey presto forward motion can be lost. Because these gears are designed to only rotate a little and pretty slowly at that, when making a turn, they have no bearings. A heavy right foot and they spin furiously as the wheel spins causing wear and slack. At some time under heavy load they, and the pin they rotate on, can snap. Not a real problem in Toyota rears but certainly the case for front diffs in late Cruisers and both ends of Discos which are pretty weak.
Your diff locks overide the differential effect locking both axles together and ensuring power is delivered equally to both wheels regards of traction. The ground conditions may mean the wheel on one side is doing nothing but with the diff lock engaged at least there is power going to the other side as well, and you will generally keep going. In many cases a 4WD in 2WD with diff lock on will do better than one in 4WD without diff lock.

FollowupID: 401954

Follow Up By: Rob from Cairns Offroad Training & Tours - Tuesday, Jan 17, 2006 at 10:45

Tuesday, Jan 17, 2006 at 10:45
Ken has given you an excellemt explanatiom. A diff gets its name by allowing two wheels on the same axle to turn at different speeds. Every time we travel around a corner the inner and outer wheels have different radius so the outer wheel has further to travel so must rotate faster, gears in a diff allow this to happen. A constant 4wd like yours effectively has 3 diffs allowing the front and rear tail and prop shafts to turn at slightly differents speeds to allow for cornering. A constant 4wd with its centre diff locked behaves just like a part time 4wd when it is in 4wd with its hubs locked. Naturally a constant 4wd should never be driven on a sealed surface with its centre diff locked. Without your centre diff locked you wont go very far offroad at all specially climbing hills as the amont of slip three diffs allow will cause the wheels with the least amount of traction to spin. Lock your centre diff as soon as you get offroad and your rear diff lock if you are in low range. Save your front diff lock for the real narly stuff as it makes the car difficult to steer. Cheers Rob
FollowupID: 402265

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