Discovery II 2003 traction control issue
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1st Gear
Joined: Mar 2019
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Discovery II 2003 traction control issue
Guys
i need your help on the below issue!
Yesterday i was driving across series on uneven humps , where i ended up in some sort of ditch terrain , the fron tire had no traction and kept on spinning freely and nothy happened even with the low gear, what is exactly happening , i dont have a diff lock , but i know there is a traction control embedded into the ABS system.
Please let me know if you have any ideas and what could be the source of the issue
Enad
i need your help on the below issue!
Yesterday i was driving across series on uneven humps , where i ended up in some sort of ditch terrain , the fron tire had no traction and kept on spinning freely and nothy happened even with the low gear, what is exactly happening , i dont have a diff lock , but i know there is a traction control embedded into the ABS system.
Please let me know if you have any ideas and what could be the source of the issue
Enad
Mudding
Joined: Nov 2018
Posts: 179
Likes: 22
From: Hickory Flat , Ga
Pro Wrench
Joined: Apr 2018
Posts: 1,516
Likes: 442
From: SE PA
I am in no way an expert in how the TC works but I too thought that the CDL was removed from the later years of the DIIs because LR designed the TC system to sense the slip and it knew when to lock it internally, which the '03 would qualify for. We all know that the only the final year got the lever back, I assumed they had a surplus of levers on the shelf and cleared them out before the LR3 was introduced in '05. I'm also uncertain how the system as a whole works. Is locking the transfer case only sending equal power through the front and rear propshafts? How do the F/R diffs determine which wheel gets the power? Are they locked or is there an LSD involved? The RAVE doesn't really go into specifics on how the power is transmitted to each wheel, however this bit from the Owner's Manual seems to indicate the TC system should prevent the OP's situation.
The purpose of electronic traction control is to maintain forward or rearward momentum of the vehicle when one or more wheels are spinning while others have good grip, e.g. if one wheel is on ice and others are on tarmac. The system works by applying the brake to a spinning wheel in order to transfer torque to the remaining wheels.
Thinking about that statement, it sounds like the SLABS ECU is determining how to force the power to the non-slipping wheel by applying brake to the slipping wheel and immobilizing it. This would force the diff to drive the other wheel, as opposed to an LSD based system which would lock up the other side through clutches. I'm not sure if this even makes sense but it's how I perceive it to work.
The purpose of electronic traction control is to maintain forward or rearward momentum of the vehicle when one or more wheels are spinning while others have good grip, e.g. if one wheel is on ice and others are on tarmac. The system works by applying the brake to a spinning wheel in order to transfer torque to the remaining wheels.
Thinking about that statement, it sounds like the SLABS ECU is determining how to force the power to the non-slipping wheel by applying brake to the slipping wheel and immobilizing it. This would force the diff to drive the other wheel, as opposed to an LSD based system which would lock up the other side through clutches. I'm not sure if this even makes sense but it's how I perceive it to work.
Camel Trophy
Joined: Sep 2017
Posts: 3,818
Likes: 1,337
From: Mission BC Canada
There are 2 separate pieces
Far better explanation - note assumes no CDL
From this site https://www.offroaddiscovery.com/201...ual-guidelines
However, it ONLY works if the system recognises that the driver needs it and it does this ONLY if the driver has his/her foot on the Accelerator/Gas Pedal. (In simple terms it says HEY! They need something and they haven’t got a foot on the Brake but they have a foot on the Gas pedal so they cant be wanting ABS or HDC so it MUST be TC they’re after.)
If a wheel now slips, the power will move through the transmission system and the differentials within that and the wheel will now receive all the power which in turn takes that same power from the other wheels.
When the slipping wheel rotates sufficiently for the TC System to recognise this the System applies the Brake on that wheel pulsing the brake on and off slowing it down until all the wheels are receiving the same amount of power. When this happens, traction on all the wheels is now regained.
BUT a Wheel has to slip and loose Traction before it is recognised and this can happen.
To understand what is happening you need to know that the Discovery 2 has THREE Differentials. One in the Front Axle, One in the Rear Axle and then a Centre One that is between the front and the rear axles. Because in Permanent 4 Wheel Drive IF a Wheel looses traction the power is transmitted through those three differentials to the wheel that is slipping as that is the one offering least resistance. (OK SO THAT BIT WAS TECHNICAL)
So we have for instance, FOUR Wheels – We have 100% of Transmission Power with 25% of it going to Each Wheel - 25%+25% on the Front Axle and 25%+25% on the Rear Axle. Because the Central Differential is what they call running OPEN, if a Wheel slips then a % of the power from each of the other wheels goes to that slipping wheel and in fact eventually it would receive the FULL 100% which means the other THREE Wheels Stop. IF you slow down that Spinning wheel back to it’s 25% then the other 75% is distributed back 25% to each remaining wheel and traction is regained. PHEW What a mouthful.
I hope you now understand that IF the Slipping Wheel is braked sufficiently then power becomes evenly distributed to each of the wheels and you regain traction.
- CDL is a center locking diff that provides equal power to the front and rear axle
- Traction control simply uses the braking system to brake a tire, in an attempt to stop wheel spin. The front and rear diff's are both open diffs stock form.
Far better explanation - note assumes no CDL
From this site https://www.offroaddiscovery.com/201...ual-guidelines
Traction Control (TC)
How does TC work?
Traction Control works in conjunction with the ABS System in both High and Low Range and it works independently on each wheel as required.However, it ONLY works if the system recognises that the driver needs it and it does this ONLY if the driver has his/her foot on the Accelerator/Gas Pedal. (In simple terms it says HEY! They need something and they haven’t got a foot on the Brake but they have a foot on the Gas pedal so they cant be wanting ABS or HDC so it MUST be TC they’re after.)
If a wheel now slips, the power will move through the transmission system and the differentials within that and the wheel will now receive all the power which in turn takes that same power from the other wheels.
When the slipping wheel rotates sufficiently for the TC System to recognise this the System applies the Brake on that wheel pulsing the brake on and off slowing it down until all the wheels are receiving the same amount of power. When this happens, traction on all the wheels is now regained.
BUT a Wheel has to slip and loose Traction before it is recognised and this can happen.
To understand what is happening you need to know that the Discovery 2 has THREE Differentials. One in the Front Axle, One in the Rear Axle and then a Centre One that is between the front and the rear axles. Because in Permanent 4 Wheel Drive IF a Wheel looses traction the power is transmitted through those three differentials to the wheel that is slipping as that is the one offering least resistance. (OK SO THAT BIT WAS TECHNICAL)
So we have for instance, FOUR Wheels – We have 100% of Transmission Power with 25% of it going to Each Wheel - 25%+25% on the Front Axle and 25%+25% on the Rear Axle. Because the Central Differential is what they call running OPEN, if a Wheel slips then a % of the power from each of the other wheels goes to that slipping wheel and in fact eventually it would receive the FULL 100% which means the other THREE Wheels Stop. IF you slow down that Spinning wheel back to it’s 25% then the other 75% is distributed back 25% to each remaining wheel and traction is regained. PHEW What a mouthful.
I hope you now understand that IF the Slipping Wheel is braked sufficiently then power becomes evenly distributed to each of the wheels and you regain traction.
Camel Trophy
Joined: Nov 2015
Posts: 3,560
Likes: 834
From: Staten Island, NY
ok, so that explains my in-practice summary above, which i had distilled from what people had reported on this forum. i guess it takes a very deft control on both the throttle and brake pedal simultaneously to redistribute power from a slipping wheel to any other wheel without having a locked transfer case.
Pro Wrench
Joined: Apr 2018
Posts: 1,516
Likes: 442
From: SE PA
^^^ Yes, and taking it further, locking the center diff (where available) ensures that 50% of the power goes fore and aft, which should assist in making sure that all the power isn’t sent to the single slipping wheel as described in that summary. In theory the TC system should do that by applying ABS to slipping wheels but the locked center diff could prevent a wheel at either end from slipping in the first place.
Rock Crawling
Joined: Oct 2018
Posts: 381
Likes: 109
From: Boiling Springs, SC
I saw an old video where they drove the Discovery up on a metal track where there were rollers on 3 corners and a lip on the front right corner.
The Discovery had zero issue moving power to the right corner and pulling itself off of the rollers.
It was quite interesting to watch when compared to others with no AWD and TC but "4 wheel drive".......
The Discovery had zero issue moving power to the right corner and pulling itself off of the rollers.
It was quite interesting to watch when compared to others with no AWD and TC but "4 wheel drive".......
Camel Trophy
Joined: Nov 2015
Posts: 3,560
Likes: 834
From: Staten Island, NY
i suspect that the performance in a situation like that would vary with the model year and the driver control. a 2004 with a locked cdl should have no problem at all, even without a skilled operator.