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Trying to understand the traction control...

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Old Jul 28, 2012 | 08:22 AM
  #1  
Externet's Avatar
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Recovery Vehicle
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From: Mideast US
Default Trying to understand the traction control...

Discovery 2000 Traction control :

Let's say the front axle is spinning on ice, the rear axle on rocky ground.
Please explain how the traction control works or confirm/correct me the way I understand it :

The spinning front axle on ice should nearly stop and the traction be directed to the rear axle.

Does it work by automatically -no driver intervention- applying brakes only to the spinning axle and then the central differential in the transfer box would put more torque to the stopped rear axle ?
Are the wheel speed sensors the ones responsible for detecting the fronts spinning and the rears stopped, signalling some computer on board to take action by applying some brakes to only the spinning-on-ice axle ?

When that automated braking happens, the TC -Traction Control- warning light at the instrument panel is turned on.

Would this mean that if one driveshaft fractures/drops off, the car will be disabled to move at all as the other remaining driveshaft will not turn, as the missing one will not have the braking effect to make the central differential in the transfer box to redirect torque to the axle with remaining driveshaft ?

To overcome the situation of one broken/missing driveshaft, if the transfer case is model prefix 41D, there is no solution as it has no locking mechanism.
If the transfer case is model prefix 42D, the solution is to crawl under the car and manually move the CDC -Central Differential Control- lever to locking position.

Also, 'converting' a Disco II to single axle drive is not possible on a 41D prefix model transfer case because the brakes automatically applied on the free wheeling axle would drag among other reasons, unless has a transfer case model prefix 42D AND signals the computer to disable applying braking when the CDC is locked.

There is no mechanical limited slip differentials anywhere in the vehicle, the trick is performed by electronic 'playing with braking'. Is that right ?
 
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Old Jul 28, 2012 | 08:54 AM
  #2  
jafir's Avatar
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From: Arkansas
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On a D2, the traction control only uses the brakes. None of the differentials have any sort of electronics or "active" features.

Even on the D3/LR3 the locking differentials are not activated "on the fly" when the wheels slipped. They are activated based on which option you pick on the terrain response dial.
 
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Old Jul 28, 2012 | 09:31 AM
  #3  
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If you want to improve your traction by a huge amount, buy and install the CDL linkage to your t/case then you can split the power, 50/50, front and rear allowing the ETC to be more efficient and giving you equal traction front and rear.
 
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Old Jul 28, 2012 | 11:24 AM
  #4  
Externet's Avatar
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Thanks.
I will take as am not that wrong and learned by studying the service manual.

..." buy and install the CDL linkage to your t/case"...

The service manual defines CDL as "Central Door Locking"

Did you mean CDC ?
Could you provide a link with details for such option ?
 
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Old Jul 28, 2012 | 12:38 PM
  #5  
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also known as central differential lock or in the King's English "centre differential lock"
 
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Old Jul 28, 2012 | 06:27 PM
  #6  
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From: Grand Rapids MI
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The trick is the wheels MUST be spinning before the TC activates.


Watch the right front tire on the blue Disco, you will see it spin-stop-spin-stop, everytime it stops it sends power to other wheels.
 
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