Tight VC demonstration.

[mattk918]

is pretty tricky to park without doing a tight turn though!

[HarryMann]

I am saying that last bit of full lock is rarely really necessary... the last 1/4 turn or so.

Also I am saying that on loose surfaces full lock is just fine, but on sticky tarmac or concrete be circumspect and rock vehicle gently if using abs.full.lock - and expect the steering to tighten up (good or bad, the VC wil be having to work hard to apportion the different axle speeds)

Also, as with any FWD vehicle, not to apply large amounts of torque when on a tight lock (on a grippy surface), if you can avoid it.

[eric]

Oh dear,
This thread is filling me with a great deal of apprehension because CJ (Syncrospares) is fitting a recon VC (from Aidan) and a re-balanced prop-shaft next Monday.

What's causing my concern is that every day I have to use full lock, both to the left and to the right, maybe a dozen or so times on tarmac.

Surely to goodness when folk bought these vehicles 20 odd years ago they would have returned them back to the VW dealership forthwith if they experienced all the symptoms described?

I'm starting to have serious misgivings about the wisdom of my endeavour to put my beloved bus back to it's original spec.

Eric.

[syncrosimon]

We need a few more comparison video's, with owners reports on how their VC's perform. My tight VC is OK turning full lock into my drive is not a problem, even when tight. I would not be too concerned. I was on Porlock hill at the weekend and the back end was wheel spinning just a bit, on the full lock turns. The up side of this is the syncro's stability in snow, ice and any other loose surface when compared to an open diff 4x4. I was following a little supped up Suzuki jeep on a steep hill in snow and ice. \He was skipping around side to side as power was going front to back without any control, causing first a wheel spin at the front then at the back, making it look very unstable. The syncro just plodded up behind with no drama. Also syncroswede was following me in his defender 90, or trying to on the snow and ice. He found that putting your foot down caused vehicle instability, again I suspect caused by the open diff situation, and just simply could not keep up. The syncro is a very stable platform, and is an exceptional off road performer as long as you dont run out of ground clearance, it does have a few peculiarities of which the tightening VC is one. De-coupling is the future of the syncro.

Simon.

[HarryMann]

Surely to goodness when folk bought these vehicles 20 odd years ago they would have returned them back to the VW dealership forthwith if they experienced all the symptoms described?

Eric, what sympton is that, specifically?

I have to use full lock every time I park and unpark on a stone surface. I just don't yank the wheel to it's abs. full extent until/unless I need to and crawl gently in/out...

Nobody's saying using full-lock will wreck anything, they're just saying to be circumspect (and be gentle with her )

Look at it this like this.... VW/SDP gave you around 1/4 to 1/5 of steering lock more than any comparable 4WD, so the Syncro has a fantastic tight turning circle.
Respect that! Would we even be discussing it if they had not gone to that trouble with nice strong wide-angle front outer CV Joints (thus requiring a couple more shuffles to get in and out of your parking spot e.g. a LandRover?)

That extra lock is fantastically handy off-road too... when something like a group of trees gets in your way.

[mattk918]

Oh dear,
I'm starting to have serious misgivings about the wisdom of my endeavour to put my beloved bus back to it's original spec.
Eric.

To put it into perspective for you, my bus has 220000 miles on the clock and the previous owner who had it 19 years claims it is still on its original VC (why would he lie?), so I don't think that you have too much to worry about! As a new owner I am just trying to get a feel for how good or bad my VC is. All the literature I can find suggests that it is pretty subjective....

[eric]

Thanks Simon, HM and Matt for your comments ..... they're greatly appreciated. I feel a lot more relaxed now.

I guess, even though I'm 58, I have lived a rather sheltered life with regard to motor vehicles and their operations, but I'm doing my best to learn. Perhaps one day soon I can persuade someone who has the appropriate lifting apparatus and knows his onions of course, to point out the various bits on the underside of the bus, explaining their function, while I film the instruction lecture.

Once again, thanks a lot fellas.

Eric.

[Syncro G]

I've done a slightly different take on the above test, sort of by accident (should of videoed it really).

Earlyer this year I breefly had one rear driveshaft off (don't ask) and so was driving it in front wheel drive. After a 30mi run (that should warm it up a bit!) I found when parking on my sloping road, when pointing down hill I could let the clutch up fully in reverse with my foot still on the brakes without the engine stalling or even lumbering too much. Letting the brakes off ment it just sat there, touching the accelerator even very slightly made it start to creap backwards - just like an automatic, rather strange in a manual!

Tried the same test from coldstart and the engine wouldn't do it! Not sure wether thats down to the temp of the VC (in theory from what others say it should have made it easyer to idle but maybe roll forwards instead of sit) or wether its [perhaps more likely] down to engine output reduiced when cold. The JX doesn't have idle speed compensation when cold so ticks over slightly slower than normal, even with the pump advanced and the glow plugs still on (which would further increse altinator demand of course). Once in reverse and reving it would settle down to sit like when warm, just not streight off.

[eric]

Glen,
Why did you have your front driveshaft off?

Eric.
ps sorry 'bout that! Hehehe.

[HarryMann]

Rear off, not front..


==More==

The 4 x 2 test

If the engine stalls then try it at higher rpm, say 1000 to 1200

If it doesn't stall and DOESN'T climb over the plank, then it's alright subjectively I'd sy

NB1. You should repeat the test carefully three of four times. If you can get it to sit behind the plank even once without stalling at idle or slightly raised rpm in G or 1st, that's a pass I reckon too...

NB. I reckon a 4 x 2 is slightly small, esp on anything but flat finished surface. So don't think a plank that's 1 1/2" or 1/ 3/4" is thick enough, I'd be quite happy if it sat behind a 2 x 3 myself

What I think matters most is that VC:

a) hasn't failed open (the other test)
b) doesn't change it stiffness behaviour dramatically from warm to very hot

NB3. I find VC can be stiffer cold than warm! - this fits with normal viscosity behaviour, that is, static friction of seals and viscous effects (thicker when cold). The 'VC effect' is more a temp/pressure transition that kicks in at about 80bar/120C

So don't judge it too harshly when cold...

[Syncro G]

Glen,
Why did you have your front driveshaft off?

Eric.
ps sorry 'bout that! Hehehe.

One end took its self off! Next time I hear a known good joint start clicking I'll stop and check the bolts are torqued up sooner! .It wasn't knocking for very long (<1km infact!), though there was sometimes a clunk when letting the clutch in which must have been an early sign, but I didn't figure that one out quick enough eather, I will now! Luckally it only bent/scrapped 3 bolts and didn't damage the hub threads.

[lloyd]

Have not owned a syncro... yet. But have owned many 4x4s over the years. Can't think of any that didn't lurch when turned tight.. with open diffs and transfer case decoupled... in 2 wheel drive. Lurching was much worse in 4 wheel drive. Most were solid axle front end, but not all. I think front end geometry (the angles the wheels turn to at full lock) is the key. Don't think they turn the same radius at full lock.. and this caused one to 'lurch' the other to keep up. Just my theory.

Having used a few VC 4x4s I found they didn't do as well as locking transfer case.

Locking differentials are best IMHO.

My understanding is a VC works like a limited slip differential. One end has to slip before other end gets power.... and even then the VC/LS doesn't transfer power equal to traction, so often there is still wheel spin. Not real 4 wheel drive. Locking diffs on axles as well as front to rear gives real 4 wheel drive.. no wheel can spin without others spinning. Drawback is can be very hard or impossible to turn when locked.

[Syncro G]

Have not owned a syncro... yet. But have owned many 4x4s over the years. Can't think of any that didn't lurch when turned tight.. with open diffs and transfer case decoupled... in 2 wheel drive. Lurching was much worse in 4 wheel drive. Most were solid axle front end, but not all. I think front end geometry (the angles the wheels turn to at full lock) is the key. Don't think they turn the same radius at full lock.. and this caused one to 'lurch' the other to keep up. Just my theory.

I've got 3 part time 4x4's here (Land-Rover) and NONE of them lurch on lock when in RWD! Same story with the UMMs, Daihatsu F50 and other things I've driven - why should they lurch when the front axle is disconected? Any windup just spinns out throught the diff to the unconstrained propshaft. One of the landys has Free wheeling hubs, (the manual type, not those crappy automatic ones, so the front axle is completely disconected at all ends), which makes the steering a little lighter when at speed though theres not a lot in it. Last time the steering shook when in RWD with the hubs locked, the front prop needed attention (A binding UJ can constrain it quite a bit)!

In 4WD they can kick really badly on tarmac but thats mainly because they have UJs rather than CV joints in the front axles, the bigger the angle they are turned the bigger the speed fluctuation and if theres too much grip so it can't just slip it out it tuggs the steering! Nearly all part time 4WD setups use UJs, down to cost I think. Most part time designs are very old, often from before FWD cars and the CV joints they require were common. Land-Rover actully started out with perminant 4WD using a pritty querky and not really very good free wheel system, and because of it were fitted with the 'Tracta' type CV joints in the front axle - the free wheel system was quickly replaced by the famous red/yellow leaver part time system but the tracta joints lasted a bit longer, though I guess an accountant spotted them and UJs took their place, that happy combo lasted over 30 years unchanged so there can't have been much wrong with it!

[lloyd]

My 4x4 history are Jeep (first was a 1953, 60, 85, 97) Chevrolet (1958, 63, 68, 72, 82), Toyota (1974), Dodge Power Wagon (WW2 vintage) and more. I lived in cold weather country and mountains. Worked on farms and in woods and needed 4x4 to get around half the time.

The lurching on them seemed to be caused by the angle the wheels were turned at full lock. One at say 40 degrees and other would be at 42 degrees at full lock. Guessing at degrees here. As one side turned other wasn't turning same amount and would lurch or squeak trying to keep up. This was only at full lock on tarmac. Obviously much worse if in 4wd. Hope that explains it better.

[..lee..]

ok getting back to the syncro. how tight is too tight and when, ie hot, cold, warm?

can a torque be applied to test them like you can do with a plate type lsd and does vw have a specific. i was thinking if you dropped off the prop and put a torque wrench on the front diff with the front wheels braked would you get a constant break point as a given temperature.

more important how tight do they have to be before it risks damaging the gearbox. if indeed its the box that goes first.

freelanders run a centre vc and they are always very tight. saying that they always blow up boxes too .

lee.