4MOTION DIFF LOCK

[Tommy Gun]

I think the confusion is arising because the T5 range (and presumably the T6 as the mechanicals don't appear to have changed much) actually has two differentials. Or, I guess three really as the front driven axle must also have one.
The two extra ones on the 4Motion appear to be as follows.
One is the centre one which is standard on the 4Motion and is electronically controlled without any driver input that decides where to send the drive to for the best traction.
The second differential is the one on the rear axle which is the one that now seems (used to be standard) to be the optional extra. This is operated by the driver with the button on the dash and locks the rear diff so that both rear wheels turn at the same rate. Hence it should not be used at speed and only where the conditions merit it's use.
This may help explain it.
http://www.volkswagen.co.uk/technology/transmissions-and-drivetrains/4motion
To confuse further there is the already mentioned standard EDL system on two wheel and 4wd which again uses the brake on individual wheels to get the best traction. This only works up certain speeds to prevent overheating. 25mph on 2wd and 50mph on 4wd.

All very complicated, god help us if it goes wrong.

Briwy,

Thanks for the detailed reponse. The extra diff on the rear axle would justify & explain the £575 price tag.

Nice one. Cheers

 

[kave]

Just to make it clear:
A diff or differential is a device that actually lets the wheels on the same axle spin at different speeds, otherwise turns would be impossible.
Therefore, a fwd or rwd car has one diff at the front or rear axle, ALWAYS.
A 4-motion Californa always has two regular diffs, one at the front and one at the rear, letting their wheels spin at different speeds making turns possible etc.
As standard, it uses the ESP and ABS to brake a wheel on one axle if it detects that on of the wheels are turning too fast compared to the other.
I first thought that a 600£ option would be something mechanical in the rear axle, but now it seems it just uses the cars regular brakes to brake the spinning wheel.
Maybe it also makes the Haldex coupling be more "locked" from start as well.
If you are going offroad I would add it for the reason you are explaining.

 

[briwy]

Just to make it clear:
A diff or differential is a device that actually lets the wheels on the same axle spin at different speeds, otherwise turns would be impossible.
Therefore, a fwd or rwd car has one diff at the front or rear axle, ALWAYS.
A 4-motion Californa always has two regular diffs, one at the front and one at the rear, letting their wheels spin at different speeds making turns possible etc.
As standard, it uses the ESP and ABS to brake a wheel on one axle if it detects that on of the wheels are turning too fast compared to the other.
I first thought that a 600£ option would be something mechanical in the rear axle, but now it seems it just uses the cars regular brakes to brake the spinning wheel.
Maybe it also makes the Haldex coupling be more "locked" from start as well.
If you are going offroad I would add it for the reason you are explaining.

Kave, yes you are correct about the diffs being standard but the extra cost is for electro/mechanically locking the rear diff not the centre one. On our 4Motion, which has the locking option, there is a large solenoid/plunger arrangement on the rear diff which is operated by the dash button.
All down to where you are going of course but we have found the locking diff to be very useful in the Pyrenees in bad conditions.

 

[SusiBus]

I spoke to the head of marketing at VW yesterday about the confusion that perspective purchases and dealers we're having with the options list and particularly the diff lock option. They have sent me this response to clarify the situation, in red below:

"The differential rear axle lock 1Y4 is available as an option in the Dealer Order Configurator, but as this was added later and so needs to be updated on the option list. The price for the rear diff lock is £470 basic ex VAT / £564 incl. VAT and it is only available on 4MOTION derivatives. With regards to functionality the rear differential lock when activated locks the differential on the two rear wheel, i.e. both wheels rotate at the same speed which makes movement slippery surface, e.g. on ice, off-road, still possible. So, for example when driving off-road one wheel has lost contact to the surface mechanical rear diff lock helps to improve manoeuvrability."

VW has informed SMG that the electronic diff lock is standards on 4motion, therefore it appears if you specify the diff lock option 1Y4 at £575 you will be getting a mechanical diff lock. As has already been raised is there any point in specifying this, after all with the low ground clearance it will never be a Toyota Amazon, a step too far I feel.

So from putting together Kave's and Briwy's post with VW's response, am I right in thinking that we now know what we are getting for our £575? - a mechanical locking of the rear differential on top of the electronic locking of the centre differential (Haldex?)

Does this electronic diff lock automatically come in when it senses the need? And the mechanical rear one only when the optional button on the dashboard is pressed?

 

[briwy]

I spoke to the head of marketing at VW yesterday about the confusion that perspective purchases and dealers we're having with the options list and particularly the diff lock option. They have sent me this response to clarify the situation, in red below:

"The differential rear axle lock 1Y4 is available as an option in the Dealer Order Configurator, but as this was added later and so needs to be updated on the option list. The price for the rear diff lock is £470 basic ex VAT / £564 incl. VAT and it is only available on 4MOTION derivatives. With regards to functionality the rear differential lock when activated locks the differential on the two rear wheel, i.e. both wheels rotate at the same speed which makes movement slippery surface, e.g. on ice, off-road, still possible. So, for example when driving off-road one wheel has lost contact to the surface mechanical rear diff lock helps to improve manoeuvrability."

VW has informed SMG that the electronic diff lock is standards on 4motion, therefore it appears if you specify the diff lock option 1Y4 at £575 you will be getting a mechanical diff lock. As has already been raised is there any point in specifying this, after all with the low ground clearance it will never be a Toyota Amazon, a step too far I feel.

So from putting together Kave's and Briwy's post with VW's response, am I right in thinking that we now know what we are getting for our £575? - a mechanical locking of the rear differential on top of the electronic locking of the centre differential (Haldex?)

Does this electronic diff lock automatically come in when it senses the need? And the mechanical rear one only when the optional button on the dashboard is pressed?

Yes, that's it exactly susibus.
We have only used the mechanical diff lock about four times but it got us out of situations where the 4Motion with winter tyres on was struggling in snow and ice. Engaged the mechanical diff lock and it pulled away without any problem. I guess what was happening was that the van sensed all four wheels were had little or no traction, as soon as the rear wheels got some grip with the diff lock on the Haldex sensed it and sent the drive to the back wheels. From memory I think the rear diff lock disengages at a certain speed to prevent damage as Kave pointed out the whhels need to rotate at different speeds on turns.

 

[Angus Morgan]

A tip I learned during a Land Rover experience day that came with my Freelander (very similar drive system), is that for the electronic diff lock to work properly, you need to increase the revs to above 2000 rpm. This forces the wheels to spin, and the breaking action is more successful. It isn't intuitive (and actually against off road driving advice for vehicles without EDL) but works very well.


Sent from my iPhone using Tapatalk

 

[Skewif]

Hello all, Having taken every variant of the T5 Cali to extreme places they really should not have gone here is my view on EDL and diff locks for what it's worth.
EDL is standard on all T5 & T6 but the name is very misleading as it does not lock any diff. EDL is very discreet and you are unlikely to ever notice when it starts to work. It's a clever electronic system that tries to reduce wheel spin and keep you moving by applying some brakes to the first driven wheel/s that looses traction. This system helps you keep moving on all relatively even low friction surfaces when wheels are starting to spin.
The diff lock you pay extra for is a real (electrically operated / engaged) mechanical diff lock on the rear axle. It physically locks the rear diff / axle so both back wheels can only rotate together. Although not needed 99.9% of the time, there is a situation when this option becomes really helpful. With 4motion if you are on very uneven ground and you loose traction / have little or no weight on one front AND one rear wheel at the same time you may not be able to move. All the drive is going to the spinning wheels with little or no traction, the EDL does its best to help but it's not really for this type of adventure. If you then engage a real diff lock on the rear axle, the rear wheel with most of the weight / traction will then become directly driven so enabling you to (hopefully) move once more. The video earlier in this thread is a perfect demonstration of this in action. If you don't have a button on your dash you don't have the rear diff lock. If you do have the button, don't push it unless you really need it.... trust me!
I think if you treasure your Cali and would never take it places where is might get damaged you probably will never need the diff lock. If you are more adventurous and ever likely to go off road along ruff, uneven, lumpy, rutted ground I'd say it's a must have because the Cali is a big old beast for my dog to push when stuck.

Seb.x

PS. I am gagging to buy a T5 SE 4motion DSG with a diff lock . If anyone has one coming up for sale, please please let me know. Any age, mileage or condition considered as it will soon be scraping and bumping along some remote track in search of the perfect spot for dinner.

 

[sidepod]

Dif locks are ok until you need to steer. They tend to induce understeer, not ideal on snow and ice covered roads. I guess the vehicle will be speed limited too with dif lock engaged?
On the Cali, which dif does it lock? Rear or centre?

I agree with GJ, if you need a dif lock then you are probably doing something you don't need to.