Even with the lowest powered and one of the heaviest of the Skoda 4x4's (108hp Yeti) and no longer driving like a hoon I would know very quickly that it was in FWD only when pulling out of a junction turning left or right in wet conditions on a less than perfect road surface.

 

The problem is that you have to undo all the self learning of throttle modulation & traction control to actually make use of the 4WD which ultimately means when stepping back into a FWD or if/when the Haldex stops engaging you will get wheelspin pulling away in the situations above like an inexperienced driver.

Yes, so there are a couple of pointers on this.  The pumps do fail very quickly if get blocked.  The Haldex system is brilliant if the gauze filter is kept clean.  Recommended every 20k miles for a oil change and filter.

 

The clutch system will not engage unless you loose traction.  I thought I had lost 4 wheel drive in the depths of snow a couple of winters back when I hit slushy stuff and was expecting the 4 wheel drive system to keep on going.  Thats completely not the way the system works.  It will firstly try and remove power first before engaging the rear clutch mechanism, if there is still a slid or lack of traction, it will then and only then engage the rear wheels.

You also need to keep the power on if the front wheels do spin, if you lift off no power will be transferred to the rear wheels. 

On 17/10/2021 at 22:49, Sargan said:

It went in for Haldex service, they advise 4WD is now working.    
Not sure how I could test it without risk of bogging it down again.

 

Floor it on slippery ground.

 

Since the Haldex Gen4 the system engages preemptively, i.e. when you start driving off or when you are accelerating from a steady speed the rear wheels will get more power through the Haldex clutch. The Haldex controller gets inputs from the ECU and even before there is slip on the front wheels the rear wheels kick in if "asked" for by the ECU. The Haldex is disengaged when braking and when the handbrake is on.

9 minutes ago, Kenny R said:

You also need to keep the power on if the front wheels do spin, if you lift off no power will be transferred to the rear wheels. 

Also true....and they don't tell you any of this when you buy the car.....

I fundamentally disagree with your assertion - "Thats completely not the way the system works.  It will firstly try and remove power first before engaging the rear clutch mechanism, if there is still a slid or lack of traction, it will then and only then engage the rear wheels"

 

As 26Dipp says it is a pre-emptive system - "i.e. when you start driving off or when you are accelerating from a steady speed the rear wheels will get more power through the Haldex clutch. The Haldex controller gets inputs from the ECU and even before there is slip on the front wheels the rear wheels kick in if "asked" for by the ECU. The Haldex is disengaged when braking and when the handbrake is on."

 

He explains it better than I could, I call it a predictive system, its seamless in use and is in operation most of the time but people don't realise because it is not intrusive, this results in suggestions of abusing the system to see if it is working, any driver with an ounce of cerebral connection to the road via the controls would know immediately if it were not functioning in wet or slippery conditions but in general be unaware of its presence.

 

You could put me behind the wheel of a car (on an open safe area) blindfolded in dry conditions and simply from pulling away in first gear I could tell you if the front or rear axle was delivering the motive force, if I were unsure it would most likely be a modern Haldex generation 4x4.

 

My Yeti has never in my ownership felt like a FWD or rear wheel drive vehicle but I did service the Haldex straight away.

Quote

You could put me behind the wheel of a car (on an open safe area) blindfolded in dry conditions and simply from pulling away in first gear I could tell you if the front or rear axle was delivering the motive force, if I were unsure it would most likely be a modern Haldex generation 4x4.

 

 

That's somewhat unfair J.R. There are many that are coming to a 4WD vehicle for the first time and would't have a clue how the system works - they just trust that it will when needed. As you rightly say, the salesman whos is selling the car doesn't give the buyer chapter and verse on how all of the systems work, mainly because they don't know.

 

It's obvious that you have far more experience with vehicles than the majority of drivers on the road and you've had a long time to learn the things of which you speak. Nowadays, folks buy a car and expect it to do what it says on the tin and if it doesn't, they get someone else to deal with the greasy bits and the modern electronics. The days are mostly gone when we used to do a lot of work on our vehicles ourselves.

I'm guessing we're of a similar age and I've held an HGV licence and driven them, plus motorbikes, cars and many types of electrically driven vehicles, but that doesn't mean that I know (and I don't) how a Haldex system works and whether it's working as it should be.

On 18/10/2021 at 08:59, Sargan said:

How ? ........ if I put car in mud, I'd have to put it somewhere  that makes front wheels slip ..... but if Haldex working rear whels would drive anyway ..... or is there a way to turn off 4WD to get it stuck ?

I I jack cae up off all 4 wheel then that would simulate slippage and if rear wheeel drive then that would prove Haldex ... but is that a relastic test.

 

Can you find an uphill bit of wet grass?  I'm fortunate, living in rural Cumbria, because we have a plentiful supply of both"grass" and "wet"!  In various 4 or "all" wheel drive cars, I have just driven along a quiet single track road until I have come to an uphill bit and put the nearside front and rear wheels on to the grass and tried to do a hill start.  I've done the same in 2WD cars as a comparison.  If you lose traction, just stop and reverse off.  You won't get stuck unless you keep the wheel(s) spinning for ages and dig yourself a deep hole.  If it passes the "2 wheels on the grass" test, and your verge is wide enough, try all 4 wheels next.  Again, it'll not be a problem because the slope of the land will help you off again backwards.

Incidentally, yesterday, by coincidence, I had to deliver Mrs. Avocet and some cycling equipment to a bike track.  To get the equipment to the side of the track, I had to drive over about 100 yards of gently, upward- sloping grass field.  It was soaking wet from recent rain, and a clay soil.  Just about the slippiest stuff known to man!  I have Pirelli Scorpions on the back and Toyo Proxes on the front - all with about 6mm of tread.  The car is a 4x4 DSG 150 bhp diesel.  I was very pleasantly surprised at how well it coped!  Even in areas where I could see the ruts from tyres that ended where other cars had got stuck.  I selected "off-road mode" but other than that, didn't do anything special.  If the rear wheels were being driven, it was utterly seamless.  I'm pretty certain they were being driven, though.  The steering was squirming a bit, suggesting that the front tyres didn't have much more to give, and I really don't believe a 2WD of similar weight would have got more than a couple of car-lengths.

On 16/09/2021 at 22:23, Kenny R said:

Apart from a strange noise when manoeuvring at slow speed with a lot of steering lock on, which I thought might be a rear diff problem, there was no warnings of any kind.

Been having this weird noise at slow speed manoeuvring and full steering lock. But the noise is present only after I have driven in wet conditions. When doing the same in dry, there is no noise. 

 

Additionally, on kick-down in the wet recently, it was as if no power was transmitted to any of the wheels. I see the engine revving , and then juddering with some weird sounds as though the transmission suddenly decoupled itself. 

 

The Haldex oil was changed at the last service , but not sure if the pump filter was cleaned. 🙄

Best ask the person that serviced the Haldex if they did, and if not have it done again, and free gratis.