So it’s the first spot of rain in a while, and I’ve had a bit of wheelspin. 
 

haldex has been serviced and the gauze cleaned. Not sure if the proper “pump learn” function has been done though, the car is on 45k miles.

 

Pulling away from lights the front spun up with traction control kicking in. Knocking/thudding was felt from the back of the car as if the rears were spinning slightly as well. 
 

I tried it again and the same happened. The road was quite bumpy. 

 
So I put the car into a few twisties and roundabouts and it is getting a bit of understeer before it sorts itself.
 

Did some launches in an empty car park with ESC off and the fronts just spun for a few seconds then the car gripped. 

Did it with ESC on and it just chirped then went.
 

Did the same on some grass and it seemed the rears didn’t spin at all with ESC on and off. 
 

it’s as if the haldex is being lazy.
 

Now I’m not sure if I’m being paranoid but what is the best way to tell, or too get it diagnosed?

 

2016 VRs diesel estate 4x4

 

cheers
 

 

 

 

Probably covered already without mentioning, but what state are your tyres in (and what are they?)

Tyres are Hankook Ventus V12 Evo2.

 

Plenty of tread on the rear and I’d estimate 35-40mm on the front left.

 

Fronts 

Just now, o6w6e6n said:

Tyres are Hankook Ventus V12 Evo2.

 

Plenty of tread on the rear and I’d estimate 35-40mm on the front left.

 

And right 

By my understanding, Haldex couple can lock up to the level that torque is evenly distributed across axles, meaning 50/50 in ideal scenario. The rest of connections are open differentials. When they say it can transfer 100% to the rear, this is just clever marketing, and although it is actually truth* (I'll explain in the end), it is incorrect to claim so, as it misleads the customers to believe rear shaft has some independent connection to the engine and full control of the torque by the Haldex system. It does not, you have additional open differential, attached to existing open differential like any normal front wheel driving car.

 

This setup is far from perfect in slippery conditions. It needs assistance to stop spinning wheel by applying braking force to stop it from spinning and save some remaining torque for another half of differential, or let's say "third" in this case.  You have felt this behavior, as it starts slapping brake pad to the brake disc, where it looses traction. Maybe it is still in the learning stage, but I suppose it is just trying to compensate worn tires on wet road. Weight distribution affects traction, when you start, from 0, most weight is at the front where engine is. When you start accelerating, more weight is transferred to the rear,  but as you get the speed weight moves back to the front. 

 

*in theory, when there is no traction, there is no torque, formula says that. So, if fronts are spinning, no torque is present there, while all existing torque is transferred to the back. This is 100%, as they claim, can happen in some conditions, but in reality I don't think so. You don't have full control over it, and you cannot with a press of a button convert such a car to the rear wheel driven vehicle. 

 

@o6w6e6n, maybe  my understanding of technical way how 4x4 is implemented to your car, can help you follow-up how it behaves on the road and is it something expected or you really suffer some malfunction. 

 

Big thumbs up for @nidza because the 4x4 system is not infalable.  When it is snowy or very wet/greasy, the haldex system will only kick-in under very specific circumstances [which they don't tell you in any blurb].  In most cases, the stablation control system will try and remove power from the drive wheels first and generally the haldex system will only kick-in if it looses traction on power delivery.  The Haldex system should generally be looked at as a 2 wheel drive - with 4 wheel traction if needed [especially the Haldex 5 system].  Haldex 3 and 4 - tend to have 30% and 10% permanent drive. 

 

Interesting reference:

 

Hi from Sweden!

 

 Just did my first haldex gen 5 service . The pump was changed 27000 km ago. And as you can see in the picture , the little filter is full of ****. So glad that i cleaned it, in with the new oil, pump the motor with vcds and fill it again. I managed to fill about 700 ml . The oil that came out was about 550 ml. I guess they didnt bother to fill again after priming the pump .