Syncro Chat: VC's, solid shafts, decouplers, AWD/4WD, etc.

[westyventures]

For non-believers in how well the VC actually works: pull out one of your rear axles, drive around without the rear locker pulled. I've done it several times - other than initial takeoff there is almost no discernible difference in power delivery. VW in fact tested the Syncro system for many miles in this manner during development. The VC is a thing of beauty and to destroy a Syncro's winter capability, flexibility, and safety factor just makes no sense to me. I've driven in excess of 50,000 miles in Syncros through snow, always VC-equipped, always with winter tires, and never once wished for a 'solid connection' as I knew the VC supplied that as needed. Several times I drove through 2'+ snow depth for short distances by accident. Many of the best modern 4x4s use a VC, because it works and allows far better control when true all-wheel-drive is needed. VW/SDP was far ahead of everyone on the curve.

[jmranger]

TL;DR

GoWesty's one-line opinion: decouple if you plan to turn the steering wheel more than 1/4 turn.

http://www.gowesty.com/library_article.php?id=627

To which I add:
including when recovering from a skid...

[jackbombay]

[Jon_slider]

[BavarianWrench]

I own this van now, http://www.gowesty.com/sale_details.php?id=661
torque biasing diffs and straight shaft. GoWesty decoupler causes bad vibration after only eight thousand miles of use. I only ran it a short time with a drive shaft installed. The straight shaft is hard on the rest of the drivetrain in turns. If you have a VC to donate I'll rebuild it and install it in the Weekender. The straight shaft doesn't make sense for Colorado winter driving. The torque biasing diffs do ok. They take a little getting used to. I may do a rebuild thread on the weekender in the link. I will need Burley, Van Cafe, a good body man, and AA transaxle to sponsor it though. It is kind of a piece of crap. VW new what was up. I have a non diff lock, VC, stock tintop too. It rips and is one of my all time favorite cars. If I get your drift soap you are thinking straight shaft for snow use? You will regret it if you need to be on the road too. Your rig will be bound up and crunchy when navigating turns. The crunchy feeling is wear on your drivetrain. If I get a VC and rebuild my Weekender I'll give you the straight shaft for free.

[alaskadan]

Last winter was my first winter in a syncro. While we had relatively little snow we had many days of smooth glare ice. My tires were studless snow tires. I was not happy with my vc. When just trying to creep forward from a stop the ass end would spin tires first as supposed to. If the van was leaning to one side or the other thats which way the rear end would slide prior to front end pulling. Didnt like it , no sir didnt like it. This summer i got stuck in a washout. Drove down into it and lined up my approach on the climb out and as i started to go for it ( crawling not broncoing) felt the ass end slip allowing it to slide sideways screwing up my line to get out. Which in turn lead to an hour of bafoonery trying get out and being dangerously close to dropping intoa big hole on the side of the washout. (Had the same tires on it).

Im still on the fence though about a vc. I understand and agree about the forgiving nature of a vc. I also take my van on the beach. This summer i went to the mouth of the kenai half a dozen times to dipnet. Never got stuck in the deep sand but came close a couple times.
Did have to bronco a bit. Fun seeing peoples faces as we went braffin by.

I have great new studded tires now and will see how this winter goes. For next summer i will getting some good ATs.

[Jon_slider]

A VC transfers some power forward, intermittently, AFTER rear wheels spin.

Link


When there is no wheel spin, I think a VC transfers a small amount of power to the front diff during straight line travel. Jed says a normal VC transfers 5%. http://forum.club8090.co.uk/viewtopic.php?f=4&t=118775

Reference:
Van cafe gives the following VC preloads.
http://www.van-cafe.com/home/van/page_109_1248/rebuilt_viscous_coupler__coupling.html
Stock 26 ft lbs,
sport 41 ft lbs, no decoupler needed,
Ultra sport 63 ft lbs, decoupler recommended.

On pavement, with no wheel spin, I think a VC is designed to slip if its preload pressure is exceeded. That suggests to me that a VC slips when a Van is in a turn. Equivalent to decoupling a solid shaft in a turn.

I think there is huge Placebo effect to using a VC. That Giddy Feeling, when you think you have All Wheel Drive. Until you actually need it and realize its not working, LOL!
_________________
My Soapboxes: Inflation; Handling; Gearing; Decoupling; Swepco

[westyventures]

A properly working VC can transmit almost 100% of torque as needed, as shown by VW in the original testing - and proven to myself in off-road travel with an unknown broken rear axle. A good way to see just how much torque is available from rest is to jack up a front wheel and attempt to turn it. Or, alternately, jack up a rear wheel and attempt to turn the main drive shaft. 5% is unrealistically low.

Re: the above video, that is a failing VC.

[Jon_slider]

[WestyBob]

[westyventures]

[hans j]

[Syncro Jael]

Ok, I took the Syncro up the canyon to drive on some snow and ice yesterday. It was a forest service road that is closed up above for the winter. I like to get out and get used to how the van performs under different conditions so I know what to expect when driving plus it is good to get ready for winter driving again without traffic. Like teaching the kids when they were young in a parking lot doing donuts in the old beetle so they could practice what to do when the vehicle begins to slide.

The road was around 5%-7% grade and glare ice where others have traveled. I always try to keep one side of the van on fluffy snow for extra bite when the roads are icy.
Speeds were in first and second gear. No traffic. I started out with all the knobs in (1)one wheel drive. Yup that drivers side rear wheel spun out on the solid ice. But I stayed in a straight track with the front wheels when it stopped.
I pulled the rear locker (2)two wheel drive and was moving again after a sideways start, then any side grade sent the rear end sideways very quickly. On glare ice it would just spin sideways until one of the rear tires got into the untraveled snow. So I stopped then only pulled the center knob to engage the decoupler and front diff. The vehicle took off in a straight line with a small amount of front and rear wheel spin. But a day and night difference from only using the rear end for traction.

So then I went off road in a field and found an incline of around a 10% grade to play on. The hill was wide enough that I could split tracks and really see the difference.

This was in about 8" of snow that is about 4 days old and has seen some sun. Not fluffy but still untraveled. It was around 40º ambient so it was easy to create ice with minimal wheel spin. The ground underneath was frozen solid.

At the bottom of the grade all knobs in (1)one wheel drive. NO GO. The drivers rear instantly spun and created ice on the snow and never moved the van. I moved over for new snow.

Pulled the knob for the rear locker (2)wheel drive. NO GO. Both rear wheels spun and the van slid sideways making (2)two ice patches for the tires to spin on. I moved over for new snow.

I only pulled the center knob (2) wheel drive front and rear and the drivers rear and passenger front spun but the van started moving up the hill but then stopped after a while. Once there was enough wheel spin the snow turned to ice and stopped progress. I tried this again with a little run before the hill and the van went right up with some signs that all wheels would spin.

I flipped around and coupled the front and locked the rear. The van again went right up the hill. So I stopped midway and tried to take off again. It spun then stopped from making ice again. While stopped I pulled the third knob for the front locker. I rolled back and the van went right up the hill with all four wheels showing some wheel spin. But had no problems going anywhere in the snow. I could really feel the fight of the steering wheel and front end trying to go in a straight line even in the snow.

My conclusions were that with a sport VC I could not tell any apparent rear wheel spin before the front diff spun the wheels. It was instantaneous in these conditions. Even though I know how the system is designed to not engage unless there is rear wheel spin. Once all three knobs were pulled all four wheels could spin on the ice with no hesitation from front to rear. Having the front diff locked would also send the entire van sideways on a sidehill where if you only were decoupled and no lockers the van would track much straighter.

When driving on snow-packed - icy conditions the VC does exactly what it was designed to do. It keeps a small amount of power to the front end all the time helping the vehicle track straighter and allowing the vehicle to be AWD. All wheels have power to them but only one front and one rear wheel will spin and those will be the ones with the least amount of traction. As soon as you lock either differential it makes the van an unwieldy beast on the highway in slick conditions. The back end breaks loose into drifting mode very easily. In a flat I locked up front and rear and the whole van could easily break loose and completely slide sideways with mild power from the engine. I would not ever recommend driving on a highway all locked up. EVER.

I think the nice thing to have is a VC that requires no operator input to function on slick roads. I can go from pavement to snow or ice and not worry about coupling up for the advantage of having the front end do some of the work. Yes, I feel as giddy in this as I do in my wife's A6 Quattro when the VC is doing it's job.

Hardcore off road... Straight shaft for sure.
I enjoy driving in the snow with the Syncro. It does very well for a 3 ton brick!

Here is my BRICK.

_________________
1987 Syncro Westfalia Hightop - NAHT
Subaru EJ25 Forged Frankenmotor, Triple Knob.
Jael = (Mountain Goat)

[shepherdsond]

Interesting thread. I have had both VC and solid shaft, currently solid. My experience, like everyone else here, is that a VC is better in snow. But a solid shaft can still be usefull. I was driving on slippery wet new snow (temp was arround 32) last weekend on Mt. Hood. On the hills in 2WD the power needed to maintain speed was just enough to slide the rear end out in corners (I don't have winter tires on yet), I found that this stopped completley when I coupled up (no VC). It was a pain though because in other areas the snow had melted off so I was constantly coupling and decoupling. I have a couple of spare VC's but I am too lazy to swap out twice a year!
_________________
87 Syncro Hightop Camper
3 knobs + solid shaft
2.2 Phase II Subaru
Hi-Top build thread:
http://www.thesamba.com/vw/forum/viewtopic.php?t=534517

[Jon_slider]

[IdahoDoug]

I'm gonna spoil the party and say no there is no power transfer to the front wheels driving on pavement that I can think of. There is no power transfer through a VC without different axle speeds. The front tires are going the exact same speed as the rears = no torque from rear. The front tires are coasting along being spun by the pavement passing under them.

The only way engaging fronts would help with crosswind stability is if the contact patch is elongated and under the tension of applied torque. Placebo effect.
_________________
1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[Jon_slider]

[Phishman068]

My VC test, which is pretty simple and foolproof proves the point of just how efficient the VC can be. On my first syncro, I first tried to move the vehicle after I fixed the engine but had left out the rear axles. Sure enough, it moved fine.
I decided to drive it around the neighborhood just as a front wheel drive and it behaved fine with no noticeable slipping or delay off the line.
I have of course sense added rear axles but it proves the point.
I have another syncro with an unknown VC in place and I am planning the same procedure with this one.

I know Ken Willford once told me about a van that drove in to his shop without rear axles. The owner had no idea! Apparently, many miles ago it was taken in to a shop to fix a rear axle and they just took them out and didn't tell him!
So sure enough, it transferred all the torque to the front and drove great!

I am a truly against solid shafts for syncros, as they simply eliminate one of the greatest design features of the vehicle while putting undue stress on the overall system. I certainly would not think it safe to run one on pavement (Which was the original question) and think that loosing the Instant AWD feature of the syncro is just a shame, particularly when in snow or mud.

Everyone is entitled to their own opinion, but I won't be doing away with a VC anytime soon!
_________________
http://www.thesamba.com/vw/forum/viewtopic.php?t=559766&highlight=winter+rust
http://www.thesamba.com/vw/forum/viewtopic.php?t=482402&highlight=sunroof+syncro
http://www.thesamba.com/vw/forum/viewtopic.php?t=569774
http://www.thesamba.com/vw/forum/viewtopic.php?p=6864936#6864936

"Along with the ability to go fast, one looses the desire to hurry."

[squeegee_boy]

[gears]

This discussion illustrates why Syncro vans in particular require GL-5 gear lube. Any binding between front & rear translates to additional Extreme Pressure on gear faces, especially R&P. Accelerated R&P wear is something I noticed straight away with the first Syncro transaxles I worked on.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com