Aren't VCs great ...solid shafters, eat yer eart out!

[syncrosimon]

have any of the turbo nutter tdi convershions ever over powered the vc? just a thought.
neil

Mike Ghia has reached the limit of the VC's capabilities with his 5 pot.

[peasant]

it is only the decupler that i engage from a stand still

So basically you've ruined your Syncro then.
You can't use 4WD on the road in all but very extreme cases and while (theoretically) more capable off-road now you won't be able to use all your extra traction because either the front or rear overhangs or the low ground clearance won't let you play with the big boys anyway.


Until now I didn't realise that the car had to be at a standstill for the decoupler to work ..but seriously and no offence meant ...that's more than useless and about the most pointless "upgrade" to a Syncro imaginable

[axeman]

it is only the decupler that i engage from a stand still

So basically you've ruined your Syncro then.
You can't use 4WD on the road in all but very extreme cases and while (theoretically) more capable off-road now you won't be able to use all your extra traction because either the front or rear overhangs or the low ground clearance won't let you play with the big boys anyway.


Until now I didn't realise that the car had to be at a standstill for the decoupler to work ..but seriously and no offence meant ...that's more than useless and about the most pointless "upgrade" to a Syncro imaginable

i think that you have mis-read my posts, i have a vc and decupler, all be it slightly tight vc, but can still pull away in g gear on full lock at tick over so not overly tight. just now i can chose when i want 4x4, i am guessing 95% of the time that i drive (i drive my van every day) 4 wheel drive is not needed, i find it very comforting that i can always get to work or where i want too go, as proven in the last couple of weeks with the snow that has just thored out, just by pulling a knob.

you can also have a donut-tastic time in snow filled carparks in 2wd with the rear locker on, but that is not very resposable now is it?

neil

[lloydy]

I thought the diff locks were best to engage when moving slowly?

[peasant]

i think that you have mis-read my posts

looks like it ...thought you had a solid shaft, no VC

[Russel]

A VC's limit is not just reached through engine power. Terrain and tires play, i would say a bigger role. Take peat or deep powdery sand with
wide aggressive tires and the resistance fed back through the VC can quite easily be to much for it even with a 1.nine TD.
VC's are good but they have their limits same as solid shafts all depend wot you want from your vehicle.

The problem with your decoupler will more than likely be the O ring used to seal the shaft. You will need to remove the actuator then the actuator bracket to get to it. Then need to change the Oring for a small oil seal and remove the lip of the actuator bracket then reassemble.
Russel

[peasant]

I thought the diff locks were best to engage when moving slowly?

Yepp ...if only for the fact that you don't want to be driving with locked diffs anywhere above G-gear speeds really ...tends to get a bit dangerous and uncontrollable then

[syncrosimon]

The problem with your decoupler will more than likely be the O ring used to seal the shaft. You will need to remove the actuator then the actuator bracket to get to it. Then need to change the Oring for a small oil seal and remove the lip of the actuator bracket then reassemble.
Russel

Aidan has rebuilt mine and replaced a bunch of O rings squeezed together with a proper seal. This made no difference. I had for 35,000miles always engaged mine at speed, including beyond 70mph. Aidan reported a little wear in the teeth on mine, perhaps this is enough to stop it engaging? But then that does not explain why after I have engaged her, she will disengage and re-engage instantly, if it were a mechanical problem then it would be a constant??

I love my de-coupler and would not be happy doing 3000mile jaunts without one. Not unless everything was brand new and refurbished.

If you use your syncro everyday for normal use they are great. For weekenders that stay close to home they are a waste of money.

[HarryMann]

Sounds like maybe the normal vacuum throttle unit might be a bit small, or the vacuum might need to be higher for a decoupler ... than that which a good serviceable difflock needs

Mike Ghia has reached the limit of the VC's capabilities with his 5 pot.

Mike's managed to reach many Syncro capabilities over the years, that's just another one then

This year it was highest ground clearance at S25Y MP, I'm sure a New Year won't stop more of our limits being exceeded

[silverbullet]

The mem'sahib used to have a Suzuki SJ410 when I first met her (ahhh!) and that used to wind up the transmission something terrible if you put it into 4wd on tarmac. I never realized that it didn't have a proper 3-diff transmission, even though it has a transfer box?
Just though that there was something terminally wrong with it...

[ericos_bob]

harryman,

Actually I agree with peasants comments as I stated in my post tarmac+cold climate = vc.

tarmac and warm climate + all other surfaces. mud,sand,dirt,gravel etc = solidshaft
reason: 50/50 power distribution all the time means 0 delay in power transfer to front wheels

Tarmac = transmission wind up in any part of the world with a solid shaft instead of a VC

Not in parts of the world where a sensible driver can drive on the tarmac in 2wd year round without ever needing the added traction of a vc. What i mean to say is you could ditch the vc in favor of the solid shaft in these parts of the world as the vc has little benefit here. Engage a solidshaft+decoupler when you venture off tarmac for superior traction.

[Aidan]

The only reason I say that you shouldn't engage on the fly at speed is there is no synchroniser in the decoupler to slow down the rotating parts and align them prior to engagement so you have two shafts one rotating at front wheel speed and one at rear wheel speed and you are trying to get a sliding collar to join the two, if they aren't aligned then something has to give and the dog teeth will get worn and flattened and engagement will become worse with time, that's why I don't recommend deciding at 40mph in the rain on windy roads to select 4wd.
I reckon that VW dropped the decoupler because it was clear that they wouldn't work properly for 100k miles in the majority of vehicles due to driver use/misuse, 100k miles is the design criteria for the vehicle and it's components, the vc just about lasts that long in most cases it seems, but if replacement is required it's just a swap out not a repair procedure

[HarryMann]

..or because extended road-testing and bench-testing indicated that the VC would last 'at least' 100K full-time use on tarmac so the expense, complication (and possible operational confusion/misuse) of a decoupler couldn't be justified.

Hence also the differential tyre tread wear provisos (and cab placard for some markets)

Also, there could have been another (additional) reason - that an engaged and disengaged 4WD vehicle could have different handling characteristics, which could lead to safety/ additional training implications. Whilst acceptable in a military or specialist marketplace, these issues would be a bridge too far in the planned domestic (leisure) marketplace.

i.e.- VW were being pretty brave in going into the 4WD market at that time, therefore minimising complexity and risk was no doubt a constant consideration during development and marketing.

IMO, this was a good and in retrospect correct executive (engineering) decision.

[..lee..]

every vehicle thats ever made is a compromise, there are obviously better off roaders available, bigger campers and vans that can carry heavier loads ect.

the syncro does everything pretty well even without a solid shaft. i guess on deep sand a solid shaft is better. it depends what you use the van for, we all tweek our vans to suit our needs a bit so i guess if you feel a solid shaft is for you then go for it, just dont throw the vc in the scrap.

i wonder if you could have both a centre vc and a centre locker. sure my other 4wd has this. ???????

[PetenAli]

Definitely not a practical approach to using difflocks... they were designed to be used on the fly, and so far have never heard of a problem caused by engaging them as and when required (although I'm sure someone could do some damage if they tried hard enough). Would have been stuck or failed ascent countless times adopting the above approach. It's often right at the top of a climb or after a sharp corner one needs the front, even in middle of sometime (climbing out of a gully). It's when they don't come on and off instantly in such conditions that compromises.

OK I can see the sense in that - when we bought our Syncro the advice from the vendor was to engage / disengage both difflocks and decoupler while stationary as a general rule. I always thought that was restricting the vehicle's capabilities. Of course at the moment I can't use the front difflock anyway. So is the general concensus that difflocks can be engaged on the move (obviously not on the motorway) and decouplers while stationary?

I love my de-coupler and would not be happy doing 3000mile jaunts without one. Not unless everything was brand new and refurbished.

If you use your syncro everyday for normal use they are great. For weekenders that stay close to home they are a waste of money.

Our Syncro is unashamedly purchased for receational purposes - I couldn't afford to run it as a daily driver because of the miles that I do for work. Now our kids are grown up and doing their own thing (although still seem to be money pits!) our aim is that our leisure time will focus around the Syncro (plus it's very useful for the three weeks per year when we have a bit of snow). Our plans include short weekends but also multi k mile trips around the UK and Europe. Thats why we went for the added expense of a decoupler.