Testing the 4WD & other bits

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Testing the 4WD & other bits

Postby Gary. » 08 Aug 2016, 21:22

I'm slowly getting nowhere with oil pressure on the Syncro Doka, though in the mean time I'd like to test the function of the 4WD system. I'm slightly concerned as I get some tyre scrub when turning on tarmac, which makes me think the rear diff lock is stuck on somehow? I think I'd know if it was the front! Update: (I've been reading http://syncro.org/how-to-fix-a-vw-syncro/. It could be the VC?) will test tomorrow.

How can I test the function without going knee deep in mud? I thought driving one wheel up a ramp would lift the other side up and this should indicate whether the diffs are locked or not?

Are there any other basic mechanical checks for the syncro's?

Apparently there is a tutorial by Jed, not found it get though? https://www.youtube.com/user/jedthespread/videos

Thanks.
Gary.

1990 Syncro doka (RHD), 1.6TD.
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Re: Testing the 4WD & other bits

Postby bene » 09 Aug 2016, 08:05

Hi gary,
I would have thought the best way to test if it is the VC that is causing the scrubbing is to remove the prop shaft.... this will then take the front drive completely out of the equation...

It sounds like the VC is 'tight' to me... is it worse if you go for a long drive then try and turn on a gravely surface?

You also need to make sure that your tyres are the same tread pattern and have the same amount of wear.

If your VC is tight, then Ian (silverbullet) can rebuild yours for a very reasonable price. (or you can risk doing it yourself). Or you can leave it as it is, because a more aggressive VC will perform 'better' off raod but then you might want to think about installing a decoupler.... but then everybody argues about that and it becomes messy and you dont know who to believe, and you end up spending so much money you have to sell your pets, everybody cries and you resent your beautiful syncro...
anyway... good luck!
My advice first off would be to remove the prop and see if you still get scrubbing.
cheers

p.s - i assume there is no light on the dash indicating the rear diff lock is on?
p.p.s check out the syncronauts website (link above in the red block) for some great difflock information (in fact just general great information)
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Re: Testing the 4WD & other bits

Postby silverbullet » 09 Aug 2016, 16:57

A good test for a running syncro is the following:

Get engine and drivetrain up to working temperature. Find an area of flat, level and dry tarmac or concrete. In first gear, drive in a tight circle (full lock) at tickover speed. Keep your foot OFF the gas!

***perform above test with NO diff locks & propshaft connected***

If the engine stalls, the VC is definitely tight. A healthy one should be largely unaffected by temperature, unless it's stone cold or freezing conditions. They ease up within a mile and only lock up when required i.e. when breaking traction. The locking should be undramatic and seamless.

Don't be scared of removing the VC, it's a straightforward if heavy job! It's easier to remove the front diff assembly complete rather than doing it in-situ. Once out stand it on it's front end using a block of wood, then remove the ring of bolts and draw the back housing off (they usually need a bit of a rattle with a mallet to free the sealant/Loctite)
The VC is a "floating" component driven by splines, so it simply lifts out of the housing.
Don't lose the spacer collar that sits between the VC and the rear housing bearing!

Now is a good time to sort it, mild weather makes the job so much less unpleasant :wink:
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Re: Testing the 4WD & other bits

Postby Gary. » 10 Aug 2016, 08:55

Thanks for the advice and pm's. I'll be running a few tests tonight and feedback on how I got on.
Gary.

1990 Syncro doka (RHD), 1.6TD.
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Re: Testing the 4WD & other bits

Postby Gary. » 10 Aug 2016, 14:51

Nice afternoon so I skipped working and run some tests. Followed this vid: https://www.youtube.com/watch?v=J6CSmQkT4Mk&feature=youtu.be Which is ideal for non-equipped diy style mechanics (like me!).

Good news is the VC performed perfectly, plus of course, while in the air was a chance to check function of diff locks - which did not work!

No lights on dash panel, so suspect faulty vacuum or actuators...

Next onto this guide:

http://www.syncro.org/DiffLock.html
Gary.

1990 Syncro doka (RHD), 1.6TD.
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Re: Testing the 4WD & other bits

Postby silverbullet » 10 Aug 2016, 17:15

All that Mike's vid demo shows is that the VC is capable of transmitting torque to the front end, not if it has gone tight. A solid shaft would do the same. The full-lock test tells you if it has gone tight, due to obvious transmission wind-up (stalling, scrubbing or skipping tyres etc)
Being a TD you need to be a little more conscious of sensing if the engine is trying to bog down, compared to a petrol motor.
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Re: Testing the 4WD & other bits

Postby Gary. » 10 Aug 2016, 17:39

Now I feel sad again :(
Gary.

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Re: Testing the 4WD & other bits

Postby bene » 10 Aug 2016, 19:29

He is the harbinger of doooooooooooooooooom!!! But you will grow to like him... ha ha!

It's good that your vc works... be happy with that.
But like Ian says, get it warmed up and full lock it and see if the engine stalls. If it does you just need to get it rebuilt by Ian and you will love it again...
Cheers
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Re: Testing the 4WD & other bits

Postby silverbullet » 11 Aug 2016, 10:34

The End is nigh I tell thee! :lol:
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