Just been looking up the latest Haldex Gen IV coupling which is fitted to the 4x4 Yeti, much more advanced than I imagined; makes the system fitted to my Golf look stone-age.

Much more familiar with it's system of control and operation when I worked in the aerospace industry.

You will now find a clutch control valve, accumulator, clutch pump and integrated ECU (which appears to be linked to just about every other system in the car) among other things inside the unit.

Great for traction and safety but I pity the bod who has to get their head round it if it goes wrong, hard on the wallet too (a 7 year Kia warranty might be handy).:eek:

All Wheel Drive - Haldex

The 4th gen Haldex is also used in the rest of the VAG group cars with 4x4 and a transverse engine these days.. So it's not all new, but it is probably a lot better/faster acting than the 2. generation which was the last one that was in use on VAG cars.

when did the 4th generation come into use eg the scout ? cheers - Stuart.

I'm not quite sure, but I think it was in build week 45 in model year 2008.

when did the 4th generation come into use eg the scout ? cheers - Stuart.

I'm 99.999% sure the Scout uses 2nd gen Haldex, as does the standard 4x4 Octy.

Don't worry about it though, 2nd gen Haldex is perfectly capable. I think the main difference is gen 4 can "pre-charge" so it can engage the clutch without having to wait for slip.

From memory, I think gen 3 was only used on a few vehicles by manufacturer demand (wasn't it Land Rover?), so gen 4 is argueably gen 3 in reality?! If anyone knows otherwise though, please correct this, I'm not absolutely sure of this

the one in the mk1 octavia doesn't have to wait for slip either with an uprated controller but what the newer ones can do is engage without movement

the one in the mk1 octavia doesn't have to wait for slip either with an uprated controller but what the newer ones can do is engage without movement

You sure about that? There are other hardware changes required (to engage without slip) that simply changing the electronics wouldn't provide?

You're right about gen 4 though; they can pre-empt slip if you floor it, for example.

yup, i have the uprated controller and it reacts to throttle position/action rather than than jsut wheel slip

Might be wrong but as I read it unlike the Gen 1-3, which produced oil pump pressure under slip, the IV has a constantly pressurised hydraulic system. The oil flow to the clutch plates being controlled by a solenoid actuated valve linked to the ECU.

An accumulator has been incorporated to help maintain oil pressure during high pump demand. The pump and accumulator form what Haldex describe as a 'power pack'.

Awesome > Haldex ECU TT/R32/S3/V64mo

Awesome > Haldex ECU TT/R32/S3/V64mo

Ah, when you said "uprated controller", I thought you were referring to the ECU, that kit is far more substantial, it contains the bits I was hinting would be needed to achieve "pre-charge" (I think Haldex call it something like that!).

To be fair, with that kit, you've practically turned the gen 1/2 into a gen 3/4

Looks like I might be delving into a Scout then, thanks for all the info, are there any problems to look out for with the haldex system ? cheers - Stuart.

The facelifted RS – the sports version of the Octavia – is

scheduled for release in May 2009; the Scout facelift is

planned for the second half of 2009.

The rundown of changes brought about by the facelift includes

a description of all significant innovations, some of

which were introduced in week 22 of 2008. This calendar

week is usually associated with the start of the new model

year, but in this case the 2009 model year for the Octavia

facelift will begin in week 45 of 2008. The information

contained in this chapter deals exclusively with the

changes introduced by the facelift and the 2009 model

year compared to the 2008 model year (i.e. up to week

22 of 2008). As the changes are the same for both body

versions – the liftback and the estate – they are described

together.

OVERVIEW OF THE FACELIFTED PARTS OF INDIVIDUAL VERSIONS OF THE CAR

OVE RVIE W OF CHANGES AS OF CALEN DAR WEE K 22/08

• New towbar control unit to connect equipment with LED lights.

• New ABS control unit.

• Fourth-generation Haldex clutch for four-wheel drive.

• Fourth-generation immobilizer

(except 1.6 FSI/85 kW, 2.0 FSI/110 kW and 2.0 TFSI/147 kW ending by calendar week 44/08).

This is scissored from the productinfo on the facelift launch, and confirms that the scout and the 4x4 uses a 4th generation Haldex as of week 22 in 2008.

Ah, when you said "uprated controller", I thought you were referring to the ECU, that kit is far more substantial, it contains the bits I was hinting would be needed to achieve "pre-charge" (I think Haldex call it something like that!).

To be fair, with that kit, you've practically turned the gen 1/2 into a gen 3/4

makes sense, i know nothing of the technical side and it was sold as an uprated ecu/controller

The 4th Generation Haldex would seem that is has the rear axle always engaged but only at about 15%? Where as I thought normally the haldex systems don't run the rear axle until it is required?

Is this true or have I got my wires crossed?

The 4th Generation Haldex would seem that is has the rear axle always engaged but only at about 15%? Where as I thought normally the haldex systems don't run the rear axle until it is required?

Is this true or have I got my wires crossed?

The Haldex schematic for the Gen 4 looks like a basic aircraft hydraulic control circuit, with a driven axial piston pump. The diagram gives the impression this is a constantly driven pump (prop shaft will probably have to be rotating to achieve pump operation) unfortunately the literature is not clear.

The earlier versions appear to have used a system where a differing rotational speed between the input and output shafts effected a cam and roller system, which would charge three oil pistons, pumping the oil into the clutch plates, the greater the difference the higher to pressure.

If the pump is being constantly driven then this could be a reason for a more permanent rear drive, plus the Limited Slip Differential I believe also takes power from the pump.