D4 Traction Control System and Indications

Quote:

---

Originally Posted by gghaggis

Even a 'permanent 4WD' system will spin wheels as you've described, as the front and rear diffs shunt torque to the wheels with the least grip. Only if you have diff lockers or a _very_ good TC system (as in the D3/D4 :BigThumb: ) will you spin all 4 wheels.

A '4WD on demand' system, if in 2WD mode, would only spin one wheel (usually on the rear axle), with no drive going to the other axle at all. Same as a std 2WD.

Cheers,

(clear as mud) Gordon

---

Hi Gordon. A diff locked vehicle will spin both wheels at the same speed irrespective of traction on the locked axle. How does the D3/D4 manage to spin both wheels at (about say) the same speed simultaneously on the one axle if one of the wheels has lost traction completely? I understand that the ETC will brake pulse the wheel that has lost traction to drive the opposing wheel with grip through the open diff, but I am not sure how that compares to diff lock or why ETC in say a D2, whilst it might be fractionally slower to act does not do the same thing?

Cheers

ETC in a D2 is not as variable. The speed and effective lock is therefore set by the necessity of having to compromise the effectiveness of the TC with the drivability of the car. As an extreme example, imagine driving on road all the time with the axle diff locks on.

The D3/4 system gives the driver the ability to vary the TC. In rock-crawl mode it approaches the locking ability of having axle lockers. You cannot drive the vehicle in rock-crawl mode unless you're in low range, hence protecting the drive systems.

The opposite is true in sand-mode. You are reducing the effective TC to allow momentum to have a greater effect. That's one reason the heavier D3 will out-perform the D2 in sand.

Unlike axle lockers, the combined TC/TR systems won't lock 100% - but close enough that you can have diagonal wheels in the air and the car will inch forward without any noticeable spin. And because the system is infinitely variable, the shock-load back to the drive train is minimal.

It is _vastly_ different to any of the preceding TC systems LR has used.

Cheers,

Gordon

Quote:

---

Originally Posted by gghaggis

ETC in a D2 is not as variable. The speed and effective lock is therefore set by the necessity of having to compromise the effectiveness of the TC with the drivability of the car. As an extreme example, imagine driving on road all the time with the axle diff locks on.

The D3/4 system gives the driver the ability to vary the TC. In rock-crawl mode it approaches the locking ability of having axle lockers. You cannot drive the vehicle in rock-crawl mode unless you're in low range, hence protecting the drive systems.

The opposite is true in sand-mode. You are reducing the effective TC to allow momentum to have a greater effect. That's one reason the heavier D3 will out-perform the D2 in sand.

Unlike axle lockers, the combined TC/TR systems won't lock 100% - but close enough that you can have diagonal wheels in the air and the car will inch forward without any noticeable spin. And because the system is infinitely variable, the shock-load back to the drive train is minimal.

It is _vastly_ different to any of the preceding TC systems LR has used.

Cheers,

Gordon

---

Cheers mate. Good read.

The interesting thing is that in deep sand towing 1.5 tonns sometimes up to 2 tonns with the D2 I have the ability to turn the ETC off the way I have set it up and just have CDL locked. Having said that i have always found the ETC to be very effective in sand, EXCEPT when starting off in deep sand from a dead stationary position. Then, without CDL engaged, it is too aggressive and works against that bounce up out of the hole to overcome the wedges of sand in front of the tyres - BUT with both CDL and ETC its a whole different story. The biggest thing in deep sand is weight and tyres every time - with gearing and torque being important also. Having said all of that my D2 V8 manual with 31 inch tyres on 16 inch rims is a tractor in sand - the original tyres tended to let them down but only increasing 1.5 inches is all that is required with 16s to make it a a weapon with CDL and ETC together. After many years of sand driving I would find it very hard to move past that combo. I think I have mentioned before towing a 2.2 tonn dual axle van into a very deep soft (no rain for a long time during the drought) cut up Flinders Beach at Straddie - road van with cheese cutter tyes..this was pre CDL for me and stock tyres and I did it in a way that made a lot of blokes shake their heads. But looking back I wouldnt try that again with the truck unlocked and without appropriate tyres. Now it would be much easier to do the same truck - the extra clearance helps too.

I would like to be in a D3/D4 at Indian Head after no rain for a month and lots of traffic. One day if I am up there and see one I am going to ask to ride shotgun because I would love to see how they go in the right hands and with the right tyre pressures. I recall once being in a particularly dry and soft Indian where heaps of people had got bogged and was waiting for a GU Patrol 4wd Ute with 33's to get snatched back to the Southern End by a Troopie on the hard sand. He was right in the middle of the pass at the Southern End about 25 metres in! I had to wait stationary in the worst part of the pass and then start off in second low range and I just drove straight through the area that he had dug up and got bogged in...you should have heard the Brit Backpackers on either ledge of the pass cheering and standing up saluting! Mainly cause it wasnt just me but my mate in a D2a V8 manual behind me who did the same trick after being stopped a car length back too. I am not suggesting that the D3/4 isnt a good sand vehicle (although to be honest I have heard conflicting reports about that) but as part of my future plans to keep the D2 or go to D4 I would not want to do that without either riding passenger or better still driving one where I like going for holidays..just in the worst patches and 5 mins would be enough to convince me one way or the other I reckon! I think the best thing is for me to join a LR club in Brissy and start going on some runs - not only for the collegiality of it but checking out the sand performance (the other performance is a given) of the later models.

Cheers

The D2 is a great 4WD, and I'm sure your's is a weapon. A stock D4 will outperform a stock D2. That's pretty common knowledge, and a simple outcome of technological evolution. It's pointless continually comparing the two systems. You do however, have a lot more options for heavily modifying a D2. If that's the sort of thing you want to do, you should stick with it.

Cheers,

Gordon

Quote:

---

Originally Posted by gghaggis

The D2 is a great 4WD, and I'm sure your's is a weapon. A stock D4 will outperform a stock D2. That's pretty common knowledge, and a simple outcome of technological evolution. It's pointless continually comparing the two systems. You do however, have a lot more options for heavily modifying a D2. If that's the sort of thing you want to do, you should stick with it.

Cheers,

Gordon

---

Gordon, not necessarily because I am not going to mod my D2 more than the very modest larger tyres and CDL retrofitted and front bar (the rest is stuff that does not help off road - roof rack, ladder etc). I am facing the future and deciding on whether to let the D2 go over 190,000 in a year or so or go to D4. I really like the D4 and I dont need much excuse, but I tow in deep sand, so I really need to do more than just assess it in deep sand by remote control. I have no doubt that the stock D4 will generally outdo the stock D2. I just wish I could take a D4 in the deep soft sand and check it out..something of course a test drive will not let me do (unless I have it for a day and risk getting it stuck!!!!). I know I have gone offtopic, but I cant help but compare the 2 vehicles in order to make up my mind on what is an expensive purchase decision.

Cheers

Quote:

---

Originally Posted by ozscott

will not let me do (unless I have it for a day and risk getting it stuck!!!!). I know I have gone offtopic, but I cant help but compare the 2 vehicles in order to make up my mind on what is an expensive purchase decision.

Cheers

---

If all you need is a mildly modded D4 for towing in deep sand (and really, almost any beach sand is deep - I suspect what you mean is 'soft'), then have no fear - the D4 will match and surpass your D2 if driven correctly. Add some decent tyres, a compressor plate and maybe some shortened rods or Graeme's LLAMS system and you're pretty well ahead of anything (that will tow) on the beach. No, I doubt you'll get any dealer of any make to let you play with a 2 tonne trailer in the sand, but re-hashing this again and again gets us nowhere - you and I have done this dance 3 or 4 times over the last 4 years - I've said all of the above before, as have others - we've tried to give you as much evidence and experience as we can, but it seems you're mated to your D2 and it's way of off-roading. Which is no bad thing, but with respect I feel this is really just wasting our time.

Perhaps someone else can give you a perspective you'll relate to a little better.


Cheers,

Gordon

Thanks Gordon. I hope you are not wasting time. I am learning every day. I have seen conflict about the D3/4 in soft sand on this very site, so you can understand my confusion. Please rest assured that I am not toying with you or anyone else on this site. I really like the D3/4 and my D2 (which as you know I love) is getting older in the tooth and I have the option of keeping hold of the dough or spending it on a D4. As a result I follow the D3/4 chat with interest both here, in the UK and in the US. I ask questions and tease out whats what. Again please dont take my comments the wrong way (have I really been interested in the new shape that long? Just shows I dont make big decisions lightly I suppose and by revisiting this issue over time I get the benefit more and more people who have spent more and more time in the new shape which has to be a good thing). I am not asking the questions (probing at times, but it would be insulting to people like yourself if my questions were superficial) to agitate. I also have to make it clear what my D2 is able to do, and what I need to equal or surpass in order to justify the change of vehicle.

Again you have been helpful in this thread and I appreciate it hence my 'thanks' expressed above to your posts.

If you think I am just wasting your time then of course you dont have to reply to my questions, but I assure you I am not.

Cheers

This has gone way off-topic, and Ozscot and I have taken the D2 vs D4 debate to PM. I apologise to the list for the wandering focus!

Cheers,

Gordon

Thanks people.

Just as a side, I haven't read anything about a D3 or D4 having issues in the sand, except under operator error.....too much pressure or DSC left on!

Mine has been awesome in the sand, even with the OEM boots and others have testified the same.

Cheers,

Kev.

Quote:

---

Originally Posted by gghaggis

This has gone way off-topic, and Ozscot and I have taken the D2 vs D4 debate to PM. I apologise to the list for the wandering focus!

Cheers,

Gordon

---

Actually it ties in quite well about me bogging my RRS last week. I have found both your discussion most informative as the discussion for and against D2/D4 has teased out a lot of information that is quite relevant in the use of both these vehicles and 4wding in general.

Cheers

Garry