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Home > Technical > Mud Glorious Mud

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Milligan Member Since: 07 Dec 2007 Location: Somerset Posts: 32

Mud Glorious Mud I drove off the black stuff through some deep mud into a field up hill, with some speed until everything ground to a halt! Got out and went shooting, home time came and all and sundry with their various Disco, Defender variants decided that I would need to reverse, turn and go out the way I came instead of driving up the muddy field and leaving by the top gate, I agreed that was probably what was going to happen with what are almost totally road tyres fitted... However I flicked the diff lock on, high ratio, no revs and let the clutch out, To everyone’s surprise including my Farmer passengers we just drove straight up the hill. The gob smacked comment of 'F$%@ me that's impressive' sums up the general reaction. What surprised me was that the Traction Control worked with the diff lock engaged - I had thought that it would not work, or work against the diff lock, there was the bang bang of the traction control. From the outside it looked good with a few comments about seeing the wheels slip and then stop and the steady slow assent... everyone was impressed… Question, can someone actually explain how the two devices work together? And why when I drove in to the field at speed why the TC seemed not to do anything? If you have a new one (with TC) and never tried pushing your luck off road do it - I was surprised at how clever this system is, there would have been little chance of my old 90 (without TC) having made it up such a wet clay muddy hill without making a mess and trying several times and with speed! 90 XS CSW... Worthy of all high praise

17th Dec 2007 9:16pm

AndrewS Member Since: 10 Apr 2007 Location: Hereford Posts: 3707

Diff Lock and TC do not work together in fact the TC does not control the engine power either. This may be the reason for diff failure I expect that on your way into the field you had enough momentum to carry you through and all 4 wheels could have been turning at the same speed. The TC will only work when you have one or more of the wheels spinning faster than the others. The drive will always take the path of least resistance so the TC will then apply the brakes to the wheels that are spinning faster forcing the drive to the wheels with grip. I think it applies the brakes 7 times a second. I also think that the Defender TC only works across the axles so you have a front and rear TC unlike the D3 which monitors all 4 wheels.

17th Dec 2007 9:56pm

Milligan Member Since: 07 Dec 2007 Location: Somerset Posts: 32

I guess I meant that they worked at the same time instead of as one system... Does this mean that the diff lock is between front and rear axles as opposed to locking the axle diff, then the TC controls each axle, thus you have the same power front and rear and then each left right wheel is controled by the TC? Can see what you mean if it's the axle diff locked then the TC will strain the diff... That's why I thought that they did not function at the same time...

18th Dec 2007 10:07am

Milligan Member Since: 07 Dec 2007 Location: Somerset Posts: 32

Been doing some research via Google and have found a couple of points... the first was that if all 4 wheels slip then traction control i.e. the slowing the wheel bit - in the Defender case applying the brake can't work. On more complex systems it reduce engine torque. So in my case because I was being brave not sensible I ground to a halt with all four wheels spinning! Then when I decided to pull away employing diff lock I gave front and rear axles equal torque and then TC applied brakes left and right etc., to brake a slipping wheel, hence we just drove up the hill... On the diff front whilst it adds the load it can't stop that load being transferred to a wheel as they only break one wheel at a time... more complex systems do both by reducing engine output as well. Maybe it's that transfer of load from one wheel to the other that is busting the diffs. Thanks Andrew, your insight was enough to understand the explanation I found. If anyone thinks this is wrong lets hear it but I think it's probably accurate and explains my scenario... It was still bloody impressive Now:- 90 XS CSW Java Black Then:- 90 CSW Oxford Blue

18th Dec 2007 9:17pm

AndrewS Member Since: 10 Apr 2007 Location: Hereford Posts: 3707

Or another way of putting it. The Defender is equiped with a centre diff lock as standard. The centre differential lock literally locks out the differential action between the front and rear axles and forces drive to be split equally between each axle for maximum traction. So a centre diff lock helps to maintain drive to some of the wheels even if one axle has lost traction. Electronic Traction Control uses the same hardware as the Anti-lock Braking System to ensure drive is delivered to the ground in slippery conditions. If ETC detects that one or more wheels are accelerating faster than the others:- it is a sign of wheel-spin. When wheel-spin is detected, ETC applies the brakes to the spinning wheel(s) and slows it down. By slowing the wheel(s) down the ETC system prevents all the drive 'escaping' through this wheel and drive transfer to the ground is maintained. In the Defender, ETC compares wheel speeds from side to side only.

19th Dec 2007 4:28pm

Milligan Member Since: 07 Dec 2007 Location: Somerset Posts: 32	This is spot on very clear... Thanks Andrew  Now:- 90 XS CSW Java Black Then:- 90 CSW Oxford Blue
20th Dec 2007 9:57am

jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8008	i though 07MY TC worked between the axles as well not just across them. will have to do some reading up. Cheers James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop
14th Jan 2008 2:45pm

AndrewS Member Since: 10 Apr 2007 Location: Hereford Posts: 3707	AndrewS wrote: In the Defender, ETC compares wheel speeds from side to side only. A Land Rover Statement
14th Jan 2008 2:48pm

jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8008	AndrewS wrote: AndrewS wrote: In the Defender, ETC compares wheel speeds from side to side only. A Land Rover Statement from where? also to add to above, accelerating improves the responsiveness of TC Cheers James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop
14th Jan 2008 2:52pm

jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8008	Yep - just looked it up, as the man says its across the axles only not between them. Cheers James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop
14th Jan 2008 3:15pm

AndrewS Member Since: 10 Apr 2007 Location: Hereford Posts: 3707	jst wrote: also to add to above, accelerating improves the responsiveness of TC
14th Jan 2008 3:46pm

Milligan Member Since: 07 Dec 2007 Location: Somerset Posts: 32

jst wrote: accelerating improves the responsiveness of TC Yep, in some respects this is correct in that the/a wheel is more likely to spin when accelerating (more revs). Also when a wheel spins it's accelerating compared to it's partner wheel. So YES in both cases the wheel will accelerate and TC is more likely to respond. However, I think you'll find that more revs does not mean your ability to move forward is improved - not slipping the wheels (the least response from TC) is the best way forward... Try it, you'll find that pulling away, you'll get to a point where a wheel slips, more revs much beyond this do nothing to aid traction. Now:- 90 XS CSW Java Black Then:- 90 CSW Oxford Blue

14th Jan 2008 3:55pm

jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8008

Hi Milligan, yes but not quite how i meant it By accelerating the wheel speed differentiation across the axle is greater therefore TC will bite the spinning wheel quicker and harder therefore the power is redirected through the diff to the wheel that has traction quicker. i agree with your comment, regarding speed and traction; the most traction is just above stall Cheers James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop

14th Jan 2008 4:14pm

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