Syncro system not working – what to try?

[scruffydubber]

Hey

Got up this morning to find a good few inches of snow, so thought it would be ideal conditions to try the 4wd, and check everything works ok.
Well on some slippy white stuff driving off in forward or reverse gears, the front whels spin, and the rears do nothing.

I had a suspicion the other day when it was wet, car didn’t seem to get the power down aswell as i thought it would.

There are no funny noises or feelings on the car.

Does anyone know whats best to start checking?

Was going to check the switch on the gear selector and the vaccuum pipes are all connected.
Although I still don’t understand fully how the system works.

The car is a G60 syncro

Thanks for any help

[scruffydubber]

Cleaned the switch contacts up. but will have to wait till tomorrow to test them with a meter.

Been reading about, and it seems the rear diff should clonk when engauging reverse, mine doesn’t do this, but the reverse lights do work.
Nobody seems to know much about the system.

[Chris S]

Not even VW UK know very much about the Golf Syncro, the system is usually very reliable & works for years!
How long have you had the car? & has it only just started doing this?

As the car is still driving (although in 2wd only) about the only mechanical part which could cause these symptoms is the VC unit, it is unlikely that anything else mechanical is broken, as usually when that happens it involves a big bang or 2 and sometimes oil all over the road.

I would suggest first putting the car in gear & jack up 1 of the rear wheels and seing if you can spin it round,(Engine off for safety) secondly then try checking the vacuum system pipes that go from the inlet manifold to the 3 ball reservior under the left front wing then on to the rear diff, my second check would be the electrics which go from the gearbox switch to the rear diff, there is also a relay & fuse in this circuit, so check for blown fuses.

[scruffydubber]

Thanks for the help chris.

I’ve only had the car around a month.
I jacked the car up on one side this afternoon, and engauged first, released the clutch slowly, and both the front and rear wheel turned.

I hadn’t checked this before cleaning the switch contacts so thought it may have fixed the problem.
So I took the car for a quick drive, and it was still the same only 2wd.

I’ll check the switch tomorrow with a meter. And I’ll have a look at the vacuum pipes. Tried to find the reservior but couldn’t. I’ll have another look.

Thanks

[Chris S]

It may be that your VC unit is not transmitting the power properly when under load, they can do this if they start losing fluid.

[scruffydubber]

I didn’t manage to look under the car today, but tomorrow
I’ll check the switch during work, can eliminate that then.
Then I’ll check the vaccuum pipes, and look for evidence of the VC leaking.

If it is the VC, will it have damaged it?
Or would it be a case of repairing the leak/seal, and refilling with correct fluid?

Thanks again

[Chris S]

No you cant repair them, you just replace the VC unit completely with another one.

[scruffydubber]

ouch, I hope its not the VC.

I have checked the switch.

And the brown and white wires close on all forward gears.
So looks like I can eliminate that.
Although I would be very interested in seeing a diagram, to check out the rest of the circuit.

I’ll check the vacuum lines next

Cheers

[no such user]

One thing you need to consider before looking to the VC is whether you were just hosing the power away through a spinning front wheel. I mucked about with my Golf Syncro in snow, as you described and was surprised at how little power there was on the ground when you accelerate. However the car still moved about just fine, until you booted it when most of the power was deployed spinning a front wheel (and sometimes a rear one too.).

VC units do wear out. The T25 units seem to go a lot more regularly than the Golf ones. This is partly due to age, but it’s my considered opinion that it’s mostly due to the freewheel, which substantially reduces the stress on the drivetrain, vs the T25. On the T25 there is no freewheel and it’s unusual that the VCs last over about 150k miles. I have a T4 Caravelle Syncro outside with 190k on the clock and my Golf is an F-plate. Maybe the Golf’s VC is about to pack up, but it’s fine at the moment.

The way VCs ‘break’ is that either they lose fluid, the fluid loses it’s viscosity, or the micro-abrasions on the plates become degraded. The symptoms of a VC failing can be a mixed bag. If the fluid goes then you’ll have no drive. If the fluid remains, but the micro-abrasions degrade then you’ll have the symptoms described in this post – when you test it the system appears to be working, but when it’s under load there is not sufficient ‘grip’ in the VC to transmit any meaningful power.

Some VCs in T25s have been known to fail ‘aggressively’ which is where they lock up way too early, which can lead to failed CVs and gearboxes – I’ve not heard of this sort of failure on a T4 or Golf.

One key factor you need to take into account when testing a VC is that that performance of the device changes with temperature – as it gets hot the fluid normally becomes less viscous, thus if you test your system at cold there may appear to be good drive, but as soon as it warms up this will stop.

With the T25s I’ve often tested VCs using the VW sanctioned method – this is done on a flat surface, using a trolley jack. You place a piece of 4″ by 2″ timber flat on the ground in front of the front wheels and you lift the rear wheels off the ground (normally on the tow-hitch). Now with the engine at idle the driver lets the clutch in with first gear engaged. The vehicle should strain at the wood, but only climb over it when the engine is revved.

Translating this test for the Golf is not difficult. Lift the front wheels of the vehicle off the ground instead and place the wood in front of the rear wheels. The biggest challenge is finding somewhere to lift the front of the car with a trolley jack!

Bear in mind if the car has been run with unequal-sized tyres, or oddly worn tyres the wear on the VC may have been accelerated.

I hope you find a solution to your problem soon

[Chris S]

The rear wheels should start to drive within one tenth of a second or one quarter of a turn of the fronts spinning.

[scruffydubber]

Thanks for all the great info.

Just had a look under the car. Vaccum pipes are present and look ok.

I have noticed fluid around the VC. When touching the fluid it is more like very tacky gel. I’m guessing this is the VC fluid, and it isn’t repairable.

I’ll get a picture in few minutes when the cameras charged

[scruffydubber]

The fluid is more like a sticky Gel, I’m guessing this is from the VC.

Here are some pics

[Chris S]

Thats the problem!

btw, If you want a new (second hand) VC unit please e-mail me as I have a spare one here

[scruffydubber]

Bugger, At least the problem is found.

I’ve sent you a message

Thanks again for all the help guys

[holmes]

i have a spare vc unit plus aload of other bits forsale i don’t know how much it’s worth however it is still attached to the diff at the moe and i have no time to remove it. if you fancy going the whole hog then i have a rear beam sandblasted and hamerited fitted with powerflex bushes and rear arms and the diff and vc unit have been cleaned and hamerited i can send pics if you wish.

[Author]

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