Electric Differential Lock

[4wheels]

My point was not 'which is superior'. My point was that all the quotes to the rules of the snow given, referred to 4WD, with no mention of AWD.

Hence my last sentence re the stroppy copper and cold mountain.

Brian R.

[IN2VWS]

Fair enough, I just don't understand why you felt the need, to tell me your opinions on which system is better.??????
Frankly, I don't really care which system is better.

[wai]

My understanding is that the 'centre diff' (ie Haldex, or VC in the older Syncros) locks up completely as soon as there is significant speed difference between front and rear axle speeds.

That's not my understanding.

As I understand it, the engine torque is sent to the end of the vehicle that can make best use of it. If the front is slipping, then a higher percentage of the torque is sent to the rear and vice versa. The diff lock then makes sure that the wheel at a particular end that can accept the best drive gets it. On a 4MOTION system, there would have to be separate diff locks for the front and rear differentials.

Also, the diff locks have an upper speed disengagement point.

[hoddy]

Have just got back from Dinner Plain / Mt Hotham. 4 nights there.
I have the T5GP 4motion with RDL button.
I found the the traction excellent, and in fact I occasionally turned off the TCS and braked really hard just to see what would happen!
The RDL button is good in sand and mud, but in snow loosing traction is a definite no-no. I was especially nervous descending and used 1st gear on the steep sections.
Snow chains are a must - I have been booked in the past - 3 demerit points

Have fun in the snow...

[wai]

The RDL button is good in sand and mud, but in snow loosing traction is a definite no-no. I was especially nervous descending and used 1st gear on the steep sections.
Snow chains are a must - I have been booked in the past - 3 demerit points

It does not surprise me. All a diff lock will do is allow the wheel with traction to do its thing. It will not and cannot generate traction. With snow and ice, you have an effective coefficient of friction of near zero as the pressure causes the ice to melt and you slip away on the melt water. Show chains bite into the ice thereby providing you with a better coefficient of friction.

Chains can be messy and difficult to fit, but they do modify the coefficient of friction. It does not matter whether you have 4WD or more. If you do not have the required friction, then no amount of wheels being driven will let you advance on snow or ice.

[Sunny43.5]

Hey Wai I agree many years ago while travelling in New Zealand in winter we were caught in a blizzard near Queenstown the police were helping people in cars get over a steep hill with their 4WD while we waited our turn {no chains} the car behind us and its trailer slide down the road backwards into an embankment as the road froze over while we waited , we were lucky as we were in a small car and it stayed put , police came pulled us to the top and off we went , all the police said was DON,T stop until we hit normal road surface again . Chains would have got us through without waiting as you say they give grip and break up the ice .Howard

[Tornado T5]

I think it was 4 years ago I remember the Mt Buller 4wd vehicles taxiing guests staying on the mountain from the carparks using chains on their front wheels. These were Toyota full time 4wds however with the iced over roads the chains were imperitive for grip and steering as Wai mentioned above.

[Ivo]

Difflocks help but its traction via friction that counts.

[Cousin]

I thought any minute he's gonna get traction and take out the camera man!

And I'm glad to see he was eventually thinking what I was, go around the damn thing



M

[Transporter]

My understanding is that the 'centre diff' (ie Haldex, or VC in the older Syncros) locks up completely as soon as there is significant speed difference between front and rear axle speeds. I know in the Syncro that used to take about 1/6 of a turn of the loose wheel. I think it is about the same in the series 2 Haldex (T5) and even less in the series 4 (T5GP). The beauty of these couplings, as opposed to the lockable centre diff on 'old fashioned' 4WD's is that they allow (quite) limited slip, sufficient for cornering, on hard surfaces when there isn't a slipping wheel, but lock up virtually immediately when there is, and so you are always in 'all wheel drive' ready for unexpected changes in surface. That's why they are so popular in rally cars. Having previously owned (and driven hard) both a 2wd and Syncro T3, I can tell you the difference in handling, even on dry bitumen, is significant. And I've never found traction to be a limitation in the T5 4M (ground clearance is a different story), either on my Cape Yorke trip, or following the T3 Syncro enthusiasts through the mud at Bateman's Bay.

A traditional 4X4 may or may not be better in deep snow, but it will be because of the better ground clearance, or more aggressive tyres, not the center diff.
Brian R.

If that would be the case, all the Touaregs would have Synchro or Haldex including these in Dakar and nobody would bother with the 4X4.

[pjondeck]

.....and what does the sheet say about AWD (All Wheel Drive) vehicles?
4motion is AWD, not 4WD.

Hi IN2VWS
Yes 4Motion is AWD, the extra $1600 or so gives me the rear electric diff lock option.
Back from the snow, didn't get a chance to find out how good it is. It never hesitated with just the AWD function. Not that I had much of an opportunity to give it a good test.
I was pulled over for a chain check in the park. I did have chains that would fit the rear wheels which would have worked in 4WD mode. I simply said to the ranger "it's four wheel drive mate", he said "oh...sorry mate, off you go". The signs do specifically say 4WD exempt and they have the prerogative to allow or not allow AWD.
cheers
PJ

[Sunny43.5]

I wonder if these park rangers are a neccesity checking out the cars etc . We drove around middle and northern parts of the US back in 97 in a front wheel drive Dodge Intrepid sedan I lost count of how many signs we passed in the Rocky Mountains [The Billion Dollar Highway] that advised chains but we never had use for them .The temperature was regularly down to freezing or less and at altiitudes of 10,000 feet with whiteout conditions and in places 4 foot of snow on the ground .
The front wheel drive felt more secure in the icy snow covered roads , having driven a rear wheel drive in NZ black ice frightened the bjesus out of me as the rear tried to overtake the front of the car several times . It all comes down to how you drive if you go gung ho then you will probably get into strife but if you take it sensibly then things should be okay. Howard