Discovery Diff-Lock

Submitted: Wednesday, Apr 14, 2004 at 07:32
ThreadID: 12023 Views:5736 Replies:3 FollowUps:6
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Hi all

A mate of mine has a Landrover discovery. About a 1998 Model give or take a year.
Its a manual transmission with the Centre Diff lock engaged by the transfercase lever. i.e push lever away from driver for Center Diff-Lock Hi or Lo range. He seems to think that he has true cross axle difflocks because his steering is affected when he has the center diff lock engaged. I know he doesnt have true cross axle diff locks but I cannot explain to him why his steering is affected with the center diff lock engaged. I havent been able to find much info on the web. If anyone could explain this well, I will direct him to this post.

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Reply By: Baldrick - Wednesday, Apr 14, 2004 at 07:54

Wednesday, Apr 14, 2004 at 07:54
The steering would be affected to a certain degree because once the diff-lock is engaged then you have 'true' 4wd. You would only really notice it on relatively hard surfaces. Does he drive on the road with the diff-lock engaged? That is a good way to damage the transmission. He certainly doesn't have cross axle diff-locks unless they have been fitted aftermarket!

The centre diff is one of the least understood, and therefore most abused parts of the 4wd drivetrain.
AnswerID: 54129

Follow Up By: Roachie - Wednesday, Apr 14, 2004 at 14:39

Wednesday, Apr 14, 2004 at 14:39
Bravo mate........I'll second that last statement. If I had a quid for the number of blokes who reckon their Prado or Landcruiser or Disco etc is equal in standard form to my ARB AirLocked Patrol, I'd be a wealthy old man.
It takes a while, but I eventually convince them by suggesting they jack one front wheel off the ground and try rotating that wheel. If it turns even though the centre diff lock is cross axle diff lock is fitted.
With centre diff lock engaged, his vehicle is the equivalent to a standard part-time patrol when it's in 4wd...(well I probably shouldn't have said that, because NO vehicle is as good as a standard patrol...LOLOL)
FollowupID: 315836

Follow Up By: Baldrick - Wednesday, Apr 14, 2004 at 14:47

Wednesday, Apr 14, 2004 at 14:47
Not quite true.

With the CDL engaged you won't be able to rotate one wheel alone, you would have to have two off the ground. ;)
FollowupID: 315838

Follow Up By: Roachie - Wednesday, Apr 14, 2004 at 15:23

Wednesday, Apr 14, 2004 at 15:23
G'day Baldrick,
I guess we'll have to agree to disagree mate.
From where I sit, if he jacks up a front wheel while the CDL is engaged, the open front diff will allow that wheel to free spin. If he had a cross axle front diff lock too (& it was engaged), then there'd be no way he could turn the raised wheel. I've deliberatly used the front wheel as an example because the back end has probably got a LSD which would limit the ability to rotate a rear wheel if lifted off the ground.
As one of the other blokes has said below, the reason he's noticing it is harder to steer with the CDL engaged (especially on a hard where did I put that bloody cheque book???) is that the front and rear prop shafts are rotating at exactly the same speed, but when he turns any sort of corner, the front wheels take a slightly different line (and travel a different distance as a result) causing the transmission wind-up that's gunna get his credit card into melt-down mode.
FollowupID: 315846

Follow Up By: Hop - Sunday, Apr 18, 2004 at 21:02

Sunday, Apr 18, 2004 at 21:02
This is exactly what happens when you jack one front wheel up on a Disco and spin it. The open front diff will rotate the front prop shaft, now if the CDL is disengaged(unlocked)and the transmission is in nuetral the front wheel will spin. When the CDL is engaged this locks the front and rear prop shafts together as if one shaft, therefore unless one of the rear wheels is off the ground the front wheel will not spin.
FollowupID: 316547

Follow Up By: Roachie - Monday, Apr 19, 2004 at 10:53

Monday, Apr 19, 2004 at 10:53
Okay, I'll admit I'm now getting out of my depth of knowledge on these matters. As far as I was aware, even with the CDL engaged, the front wheel which was lifted off the ground should still spin due to the actions of the open front diff. It's got me beat??????????LOL
FollowupID: 316617

Follow Up By: Hop - Monday, Apr 19, 2004 at 20:28

Monday, Apr 19, 2004 at 20:28
Try it on your patrol, jack one front wheel up, with your front diff lock disengaged turn the wheel, you will notice the front prop shaft will spin. If you lock the front diff the wheel will not spin.
FollowupID: 316723

Reply By: Rosco - Bris. - Wednesday, Apr 14, 2004 at 08:44

Wednesday, Apr 14, 2004 at 08:44
As Baldrick has said .....

All constant 4WD vehicles, whether off road or not ... and that includes the likes of Porshe and Subaru WRX have a third (centre) diff to allow for the different radii curves traversed by the front and back axles. It has absolutely nothing to do with locking the front or rear diffs.

Locking the centre diff merely converts it to direct drive ... much the same as engaging 4WD in a non-constant 4WD vehicle. The standard front and rear diffs are both still slipery.

Your mate should only notice any difference if he's driving on a hard surface with the diff locked .... and if so he should practice tearing up $100 notes.
AnswerID: 54136

Reply By: Member - Cruisin (QLD) - Wednesday, Apr 14, 2004 at 21:13

Wednesday, Apr 14, 2004 at 21:13
I think we have enough explanations here to direct my mate to this Post.

Read it and weep Billy Boy !!
AnswerID: 54259

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