Club 80-90 Forums

I stumbled across this little snippet while reading up on Torsen diffs and the like on Wikipedia, under quattro:

"The Haldex Traction LSC centre coupling is often used as upgrade to an aftermarket four-wheel drive conversion on older front-wheel drive Volkswagens. It is said to be capable of withstanding larger power outputs than the also commonly used viscous coupling system from a syncro vehicle.

The conversion is carried out by way of a viscous coupling rear axle and associated live suspension system from a syncro vehicle being fitted to a suitable project car (i.e. a Volkswagen Corrado or Volkswagen Golf), and then fabricating a custom bracket to hold the Haldex rear coupling.

Enthusiasts often either use the OEM ECU and engine management from a newer Volkswagen Group car to control the Haldex centre clutch using the standard ABS road wheel speed sensors - or can buy aftermarket controllers that supply the relevant pulse-width modulation to actuate the clutch and transfer drive to the rear wheels either via simple variable dial or based on throttle position sensor (TPS) calculations."

Could be an interesting avenue. Using a simplified Haldex system with just engine and road speed input maybe?
There aren't any references and a google turns up far too many boy racers wanting to build R32 powered Jettas...

Then I found this at All Wheel Driven, for those who like it complicated...interesting used of a vc on the RH end of the centre diff.
No wonder they were so awful to service!
Our syncros scarely get a mention under the VW page http://www.awd.ee/article.html?inc=vol" onclick="window.open(this.href);return false;

I've always had in the back of my mind either a Haldex or Torsen system instead of a VC. The whole gubbins in not very big and is capable of huge torque and power. Its a lot more advanced than a VC in many ways

I don't know if the Torsen Diff could be persuaded to work as a limited slip coupling. Maybe it could be made to function "one-sided" like a VC, if it were coupled to a multi-plate clutch on the free end? I don't know enough about their behaviour, other than it being a cunning application of worm/wheel torque reaction.
A Haldex coupling would involve some electrickery but if it could be made to function with the bare minimum it could be a winner. But it could live outside of the front diff, which would be a good thing.

But it could live outside of the front diff, which would be a good thing.

what's good about it ? Something else to attach to the drivetrain and protect especially if it's got electricery

KISS

afaik noone has come up with a better system for our vehicle and since we can get everything either new or remanufactured or refurbished there's no need to reinvent the wheel

sorting out a good syncro uk solution to scoobie installation makes sense but trying to reengineer the drivetrain doesn't, our system works, works well and does what it says on the tin

Aidan, this was supposed to be a light hearted technical discussion and an excuse to point 4wd fans to the allwheeldriven site for those who haven't seen it before. I do find some of it makes for thought provoking reading, this being taken from the Viscous Coupling page:

"The disadvantage of a viscous coupling is that it engages too slowly and allows for excessive wheelspin before transferring torque to another wheels. This is especially critical in automatic all wheel drive systems - when cornering under acceleration, the rear end is engaged with a slight delay, causing sudden change in the car's behaviour fron understeer to oversteer. Also, when taking-off in sand, front wheels can become bogged down before all wheel drive is engaged.

In an attempt to reduce the coupling's activation time, VW Golf MkII Syncro always transfers 5% of torque to rear wheels (this is achieved by rear driveshaft rotating slower than front driveshaft in normal conditions, causing viscous fluid warm-up and slight solidification)"

Like I said, interesting reading!

This has been discussed in great depths before...

Still yet to see anyone with enough cash and motivation go and do it...

I'd like to see where and what car they based their arguments on as to how slow the VC works.. as anyone that has been watching any T25 syncro closely will testify, there aint usually a lot of wheelspin before the VC kicks in... + the other factor is 1 output of an open diff will keep spining even when 50% power has been transfered to the other axle.. thats not the VC's fault....

Yes I will conceed that a billet shaft make s a lot of sense and works better in sand... going to do a lot of sand driving in the outbacks of Woking are we

OK.. lets find some test vehicles and do a propper quantifiable set of tests....

Well...as it happens we have quite a lot of sand on our doorstep - it's called "Sandpit" and was the one mentioned by HG Wells in "War of the Worlds". Local boy done good Might upset Horsell Common Preservation Society if I go cutting the chains on the gates to go dune hopping at night

Solid shaft / non VC transmissions are for the desert rats like Herr Winkler, not wannabe rock-hoppers and mud-pluggers like me in the UK

You know I'm not being serious about all this, just thought that the AWD site might be of interest to someone else?
OK I am an anorak. I admit it. I love a good technical manual, me

you really do need to get out more Ian.....

Lets find a frelling carb to slap on the old girl and get it MOT's...... could come over 1 eve nex week, if I can crash out on a floor or summat..

If you like the idea of sleeping with the dogs - they will fight you for sofa space
Are you working local-ish now? Pasty White said you were back to a so -called proper job...

I have an Aud 80 quattro (with Torsen) as well as the Syncro and used both of them quite extensively in last winter's snow. (I have a very steep driveway so wouldn't have got out with a 2WD car)

Some interesting (but not very technical) observations:

The quattro system is more sophisticated on paper but both seem to work equally well when it comes to sheer traction - I had great fun in both vehicles driving around stranded, wheelspinning 2WD cars (and it was especially satisfying when they were powerful, expensive models....)

I have noticed that the Syncro's VC system suffers from transmission wind up/ tyre scrub when manoevring in tight spaces whereas this seems entirely absent with the quattro.

The car, with it's smaller road tyres occasionaly needed the diff lock to progress but the van never needed them (just as well - they are inoperative at the moment)

The van has this requirement for the tyres to all be the same size to protect the VC, hence the need to rotate wheels every 3000 miles, but this is never mentioned for quattros. This is my second quattro; I previously ran a 1985 90 quattro for 100,000 miles with no problems.

The 90q had a TSR engine conversion (about 170bhp) and the quattro traction was invaluable in many road-going situations. The van is not that kind of vehicle (!) so the traction is only really used for exiting sticky situations.

I have personally never noticed any delay with the VC taking up the drive to the front wheels. In snow, ice or mud it just goes.

I have noticed that the Syncro's VC system suffers from transmission wind up/ tyre scrub when manoevring in tight spaces whereas this seems entirely absent with the quattro.

is this because they are only 2wd in reverse ?

Quattro isnt Aidan, thats the Golf (maybe passats etc too) syncro you are thinking of...

Quattro in the original version (in-line engines) is proper full-time 4WD system with 3 diffs all working for a living, unlike some of the Haldex-coupled transverse engine offerings that are variously badged as quattro and 4motion by VAG. They are indeed FWD + part-time rear wheels, like a T3 syncro but the wrong way round

My young lad has a Passat 130TDi 4motion and he gets no transmission wind up whatsoever and its almost impossible to tell when you are in 2 or 4 wheel drive. However, because we are both children, we did do a test comparing a FWD Passat 170TDi with his Passat 130TDi 4motion over a well known road section local to where we lived (Toomanytoys might remember the roads around my house) at the time. This test was probably as unscientific as you can get but it proved a number of things.

1. We were completely nuts to travel at the speeds we did but G*d it was fun
2. Driving very quickly out of certain bends - and they needed to be reasonably sharp - you could see the 4motion pull cleanly out whereas the 2WD was scrabbling/understeering
3. The road surface was dry and the faster we went the greater advantage the 4motion had. Please note the speeds were well over what Syncros will max out at
4. Switching off the 'traction control' didn’t alter the findings, just slowed things up a bit

We concluded that the 4motion system in that car is brilliant for fast road driving without any of the limiting factors that the VC has in a Syncro.
Soon afterwards we had the opportunity to compare the Syncro and the 4motion in the snow and ice. The limiting factor was the ground clearance on the Passat so the test was brief as the snow was in excess of 6” deep. The 4 motion was able to go anywhere the Syncro could until the snow build up caused it to get stuck. Again the 4motion showed its brilliance.
I would love to see someone ‘do a 4motion T25’ cuz I reckon it would be very good indeed. I wonder how it would handle diff locks?

silverbullet wrote: They are indeed FWD + part-time rear wheels, like a T3 syncro but the wrong way round

What gives you the idea that a Syncro is part FWD or 4 x 3 and 1/2 ?

This is of course non-scientific, but I have driven both a 2WD TD and my Syncro TD on the same bendy and bumpy roads around my locality in a "sporting" manner (that is to say as "sporting" as a 1.6Td can reasonably be ) and let me tell you that in tricky bends in the dry and normal (normal for Irish country boreens) bends in the wet there is a major difference in driving the Syncro.

There is nothing like the FWD just kicking in after the rear end has already gone critical, it doesn't feel part time or half-arsed either. The 4WD is very much permanent and it very much works.

It may well be that on some sand dune in the Sahara the front wheels start turning that little bit later than the rear wheels ...but on the road, at speed, the system works juuuust fine.