Viscous coupling silicon

[sandwedge]

Automatic 2.5 tons or there abouts, probably have a bigger turning circle due to wide tires.

[HarryMann]

Automatic will also disguise any tyre scrubbing and 4WD turning drag (if any)

If you get the chance, do the 2x4 plank test or brake roller test, to make sure the VC will slip properly at low speeds and loads

[jebiga41]

After being at Dorfbrunnen's and getting the grand tour and more besides From watching the results of the tests (one stiff vc went off the scale at 15degrees i.e vertical it started at 260nm) he really knows what he is doing and you really don't want to try this at home or run a very stiff vc. The best would is that it would fail open and leak leaving no 4wd the worst being its too stiff wrecking your gearbox.

Dimethicone is another name for polydimethylsiloxane and is used to impart a soft velvety feel to hair or skin products.

so thats your secret clive

[HarryMann]

so thats your secret clive

No, but it will be, my order's in !!

[syncropaddy]

The 4motion setup is undetectable hot or cold because all of the applications are 'based' if you like on 2wd gearboxes. What I mean is that the drive on the 'steering ' wheels comes directly from the gearbox and the 4wd bit of the system goes to the rear where the Haldex or Torsen magic bits are. If there was anything to 'feel' (like that which we feel in the Syncro) it would be at the back. In essence the modern layouts are the reverse of the layout in our Syncros leaving us with this 'feel in the steering'.

Some stuff I found .....

The Haldex Differential

The Volkswagen 4MOTION all-wheel drive system is a key technology in sporty, but above all safe driving. At the core of this method of power transmission to all four wheels is the Haldex coupling. The Haldex coupling is mounted in front of the rear axle differential and actually becomes part of the rear differential case. Yet, it functions as a centre differential. Its hydraulic and electronic systems automatically detect wheel slippage (for example, due to road conditions or high power requirements) and distribute the tractive force to the two axles accordingly.
Haldex Centre Differential
And because it‘s so fast in slip detection, in the absence of wheel slippage, this system defaults to front-wheel drive for better fuel economy and less wear on the drive train. When driving the Golf R32, you hardly notice the work of the 4MOTION Haldex system. You only feel the absence of under- and oversteering. Even on wet roads or when accelerating quickly out of tight curves, there is no noticeable wheel slip, and extreme spurts do not cause the steering to jerk. In addition you do not feel any wind-up in the drive train when maneuvering into tight parking spaces.
The development of the Haldex differential is a giant step forward in modern all-wheel-drive technology. It is controlled based on the inputs the Haldex control module receives from the vehicle. Slip is no longer the only decisive factor in the distribution of drive forces; the car‘s dynamic state is also a factor. The processor accesses the ABS wheel speed sensors and the engine control module for data that provides the processor with all the information it needs. This information includes road speed, cornering, and coasting or traction mode — all of which allow the Haldex system to respond optimally to any driving situation.

The Haldex centre differential is mounted on the rear axle differential and is driven by the prop shaft. Engine torque is transmitted through the gearbox to the prop shaft. The prop shaft is connected to the input shaft of the Haldex differential. In the Haldex differential, the input shaft is separated from the output shaft to the rear axle differential. Torque can only be transmitted to the rear axle differential when the Haldex differential clutch plates are engaged. In the absence of wheel slippage, the clutch plates are not engaged, and only front-wheel drive operates until power is needed for the rear axle

The 4MOTION Haldex system results in the following advantages:

* Permanent all-wheel drive with electronically controlled multi-plate clutch
* Front drive characteristic (distributes power to the rear axle only when needed)
* Quick response time
* No strain on clutch when parking and manoeuvring the vehicle
* Compatible with different tires (e.g. emergency wheel)
* No restrictions on towing with the axle raised off the ground
* Fully combinable with traction control systems such as ABS, EDL, TCS, EBD and ESP

The TORSEN Differential (Passat B5)

The 4Motion system relies on the Torsen© centre differential to distribute power between the front and rear axles. Torsen stands for TORqueSENsing differential. The biggest advantage to the Torsen differential is that it works without driver input. There are no electrical connections or computer controls. The Torsen differential is a sealed unit and is located in the rear of the transmission case.

The Torsen differential is composed of the following components:

* Differential housing
* Planet gears (with spur gears)
* Front axle side gear
* Rear axle side gear
* Front driveshaft
* Rear driveshaft

Inside the Torsen housing, there are pairs of helical planet gears. The planet gears are held in tight-fitting pockets inside the housing, and are splined together through spur gears at their ends. These spur gears do not allow the planet gears to rotate in the same direction. The teeth on each of the planet gears mesh with the teeth of one side gear. When the vehicle is moving in a straight line with no slip, the transmission drives the Torsen unit. The Torsen unit in turn drives the planet gears, which drive the side gears.

When an axle loses traction, the planet gears, through the spur gears, are responsible for the power transfer. The interlocked planet gears will apply even force to each side gear. Only the planet gear meshed to the side gear that has traction can apply this force. The other planet gear is simply following along. The maximum amount of power that can be sent to the axle with better traction is determined by the Torque Bias Ratio (TBR). TBR is determined by the angle and shape of the teeth on the side and planet gears. The TBR of the 4Motion Torsen differential is about 2:1. This means that about two-thirds of the torque, or about 67%, can be sent to the axle with better traction. The remaining third is sent to the other axle.

There are other types of centre differentials in production vehicles. Hydraulic and viscous are common, as are lockable differentials. The Torsen differential transfers power to both the front and rear differential. These are not locking differentials. Electronic Differential Lock (EDL) is used to control slip at each wheel.

And finally .....

A hydraulic differential uses a set of common bevel differential gears with a set 0f clutches attached. There is also a hydraulic pump, which is activated by wheelspin. This pump builds pressure, which operates the clutches, locking the differential. This stops wheelspin.

A viscous differential uses two sets of opposing plates attached to a set of bevel differential gears. The plates operate in a silicon fluid. Alternating plates are attached to the housing and output shafts. The fluid changes viscosity rapidly in the presence of heat and pressure from the spinning axle. This causes the opposing plates to transfer torque from those that rotate faster (spinning axle) to those that are rotating slower (axle with better traction) by viscous shear force. With high slippage, the differential can lock almost completely.
Disadvantage: The response time of the viscous coupling is slower than that of the Torsen differential. The Torsen offers nearly instantaneous power transfer.

So, how long will it be before we bin the viscous couplings and fit Torsen diffs?

[syncrosimon]

The answer is simple, de-couple.

[syncropaddy]

The answer is simple, de-couple.

Well as Dave demonstrated at SP recently, de-couplers dont always work particularly when you dont use them often.

[KarlT]

Okay, you've all convinced me...Its not a job for me & the mrs cookery measure cups!
If some refurbs are breaking down after a couple of years, maybe new/original is the answer. But does that mean they have been sat on a shelf for 20 years? If so, It can't be good for them.

[syncropaddy]

http://cgi.ebay.de/VW-Bus-T3-T2-Syncro- ... 286.c0.m14" onclick="window.open(this.href);return false;

[SYNCROSPARESUK]

Hmmm, interesting, we have got quite a few VC's and can now tell good from bad with a few simple bench tests, condition of fluid, turning force etc. We are in the process of looking into re furbishing but will need to find some one with the test equipment in the UK....when we have found that person or company we should be able to supply.

Did you know service life of VC only 65,000 miles.

[toomanytoys]

but will need to find some one with the test equipment in the UK....when we have found that person or company

Dont want to pee on your parade, but good luck....

We (80-90) found Dorfbrunnen (spelling ) via a chap in the UK (Cav16) that had tried to refurb and find people years ago.. he is/was specilising in Calibra 4x4 drivetrains.. that was quite a few years ago.. apparently the only ones that made and had the equipment were SDP in Austria, they sold the biz and equipment to Dorfbrunnen.. there may be some alternative out there now, but i'd expect the investment to be so high it isnt worth it.. but tell us if you make any progress on it... it would be much handier to have a UK source as the carraige is the killer I think...

[syncropaddy]

Did you know service life of VC only 65,000 miles.

Interesting ..... tell that to the one in my Syncro! Its got 275,000 kms on it and still works just fine.

What simple bench tests are you using? I would think that unless you have the correct equipment and are testing at the correct temperatures etc, your data and conclusions may not be correct. How do you know from looking at the fluid that it is good?

[Aidan]

there's a set of the test equipment at the GM training facility apparantly, or was......

[Titus A Duxass]

Did you know service life of VC only 65,000 miles.

Interesting ..... tell that to the one in my Syncro! Its got 275,000 kms on it and still works just fine.

The quoted life of 65,000 miles is actually quite worthless without knowing how it was calculated and what batch sample size was used.
Yours has lasted 275k and some could have gone kaputt in 10 miles so the mean could still be 65k.

65k is probably a figure that VW felt comfortable with.

[syncropaddy]

Did you know service life of VC only 65,000 miles.

Interesting ..... tell that to the one in my Syncro! Its got 275,000 kms on it and still works just fine.

The quoted life of 65,000 miles is actually quite worthless without knowing how it was calculated and what batch sample size was used.
Yours has lasted 275k and some could have gone kaputt in 10 miles so the mean could still be 65k.

65k is probably a figure that VW felt comfortable with.

I would imagine that the figure of 100,000 kms was arrived at by Steyr Puch after considerable testing. I also imagine that the figure varies considerably with the type of use and is a benchmark figure for acceptable usage for both the customer and for warranty claims. I would also consider the fact that this figure is for new units and not refurb'd ones as the original manufacturer would have performance parameters to adhere to in production testing. VW would have no control on the quality of aftermarket refurbs so would not issue any figures.