Decoupler Fault

Hi All


The problems never seem to end...

Today I placed all 4 wheels of the ground on jack stands, ran the engine in first gear.

The rear wheels turned (as you would expect) then I pulled the decoupler switch.

The green light came on (saying that the electrical switch on the decoupler operated).

However it did not engage as in the front wheels did not turn.

I jumped out and rotated the front wheel by hand but it still would not engage.


Any ideas?


Peter

Hi Peter,
Bit of a worry.
Maybe the VC function has died ... gone fully passive?
Ken

On 8 Sep 2015 14:52, "kestel.p@bigpond.com [Syncro_T3_Australia]" <Syncro_T3_Australia@yahoogroups.com> wrote:

Hi All


The problems never seem to end...

Today I placed all 4 wheels of the ground on jack stands, ran the engine in first gear.

The rear wheels turned (as you would expect) then I pulled the decoupler switch.

The green light came on (saying that the electrical switch on the decoupler operated).

However it did not engage as in the front wheels did not turn.

I jumped out and rotated the front wheel by hand but it still would not engage.


Any ideas?


Peter

Hi Peter,

When you lift all 4 wheels and engage the decoupler, at least you drive shaft should spin. If this doesn't turn, than you got a problem with your Decoupler. If it spins, than your VC is dead (what I think that's the problem).

Cheers Arne



Am 08.09.2015 um 15:59 schrieb Ken Garratt unclekenz@hotmail.com [Syncro_T3_Australia] <Syncro_T3_Australia@yahoogroups.com>:

 

Hi Peter,
Bit of a worry.
Maybe the VC function has died ... gone fully passive?
Ken

On 8 Sep 2015 14:52, "kestel.p@bigpond.com [Syncro_T3_Australia]" <Syncro_T3_Australia@yahoogroups.com> wrote:
 

Hi All


The problems never seem to end...

Today I placed all 4 wheels of the ground on jack stands, ran the engine in first gear.

The rear wheels turned (as you would expect) then I pulled the decoupler switch.

The green light came on (saying that the electrical switch on the decoupler operated).

However it did not engage as in the front wheels did not turn.

I jumped out and rotated the front wheel by hand but it still would not engage.


Any ideas?


Peter

Maybe a vacuum leak and set at disengaged ?

On Tue, Sep 8, 2015 at 2:52 PM, kestel.p@bigpond.com [Syncro_T3_Australia] <Syncro_T3_Australia@yahoogroups.com> wrote:

Hi All


The problems never seem to end...

Today I placed all 4 wheels of the ground on jack stands, ran the engine in first gear.

The rear wheels turned (as you would expect) then I pulled the decoupler switch.

The green light came on (saying that the electrical switch on the decoupler operated).

However it did not engage as in the front wheels did not turn.

I jumped out and rotated the front wheel by hand but it still would not engage.


Any ideas?


Peter


As Arne said, if the decoupler works the tail shaft will turn. I would also expect even a failed VC would drag enough to turn the front wheels when your up on a stands.

Does the light come on reliably when switching on/off? This would indicate the selector shaft is moving as it should and the vacuum unit and switch are also working. You could also take the switch out and confirm that is working and see the selector shaft moves also.

If the selector shaft is moving fine, then it indicates something is wrong further inside.


Silly question maybe, but I assume neither front wheel turns?


Richard

on could make sure proper vacuum is getting the decoupler vacuum connection.
..before digging deeper.

though one would think ..it the light on the dash says the right thing ..
the parts that move inside the decoupler housing to operate the light ...that should say it's working externally and moving that switch-affecting part inside.
At least it's not to hard to take the decoupler off the front of the trans.

I was surprised ..on the last one I installed anyway ....pretty sure it's like this :
the default ( like if vacuum isn't working ) position is 2WD ..thought that was weird.
I'd want the default 'swithching-mechanism-not-working' to be AWD.

so if it breaks ..you're back to AWD as original.

In my opinion many german automotive things are designed to work right only when they ARE right ..
I it's going to fail ..you'd want the decoupling ability to fail, automatically reverting to AWD.
Safety issue even.
Like get out of really bad boonies issue.


On 9/8/2015 2:04 AM, cathrich1@yahoo.com.au [Syncro_T3_Australia] wrote:

As Arne said, if the decoupler works the tail shaft will turn. I would also expect even a failed VC would drag enough to turn the front wheels when your up on a stands.

Does the light come on reliably when switching on/off? This would indicate the selector shaft is moving as it should and the vacuum unit and switch are also working. You could also take the switch out and confirm that is working and see the selector shaft moves also.

If the selector shaft is moving fine, then it indicates something is wrong further inside.


Silly question maybe, but I assume neither front wheel turns?


Richard


Scott,

I would totally agree with that - unless you also had the issue of a tyre that was mismatched for some reason and you had to drive for a while before you could get a properly matching tyre. 4wd would damage the drive-train in that situation and 2wd would not.

But I would rather as you suggested - automatically revert to 4wd not 2wd.

Cheers,

Skot

On 9/09/2015 9:33 AM, 'SDF ( aka ;jim lahey' - Scott ) ' ScottDaniel@turbovans.com [Syncro_T3_Australia] wrote:

on could make sure proper vacuum is getting the decoupler vacuum connection.
..before digging deeper.

though one would think ..it the light on the dash says the right thing ..
the parts that move inside the decoupler housing to operate the light ...that should say it's working externally and moving that switch-affecting part inside.
At least it's not to hard to take the decoupler off the front of the trans.

I was surprised ..on the last one I installed anyway ....pretty sure it's like this :
the default ( like if vacuum isn't working ) position is 2WD ..thought that was weird.
I'd want the default 'swithching-mechanism-not-working' to be AWD.

so if it breaks ..you're back to AWD as original.

In my opinion many german automotive things are designed to work right only when they ARE right ..
I it's going to fail ..you'd want the decoupling ability to fail, automatically reverting to AWD.
Safety issue even.
Like get out of really bad boonies issue.


On 9/8/2015 2:04 AM, cathrich1@yahoo.com.au [Syncro_T3_Australia] wrote:

As Arne said, if the decoupler works the tail shaft will turn. I would also expect even a failed VC would drag enough to turn the front wheels when your up on a stands.

Does the light come on reliably when switching on/off? This would indicate the selector shaft is moving as it should and the vacuum unit and switch are also working. You could also take the switch out and confirm that is working and see the selector shaft moves also.

If the selector shaft is moving fine, then it indicates something is wrong further inside.


Silly question maybe, but I assume neither front wheel turns?


Richard



The drive shaft does not turn. Not a VC problem.
The electrical switch works fine. I disconnected it and the light stayed off.
This says the mechanism inside is moving to some degree, however it doesn't engage.
Today I will take the syncro off the stands and go for a drive. Maybe that is all that is needed...hopefully.
It has been on the stands for 3 months now during the full renovation and just maybe, the mechanism is a little stuck.

Will report back.

Peter
Lube and clean the actuator shaft where it enters the housing whilst manipulating it manually. When you are finished put a smear of marine grease on the shaft. Greg E

From: "kestel.p@bigpond.com [Syncro_T3_Australia]" <Syncro_T3_Australia@yahoogroups.com>
To: Syncro_T3_Australia@yahoogroups.com
Sent: Wednesday, 9 September 2015, 10:27
Subject: [Syncro_T3_Australia] Re: Decoupler Fault

 
The drive shaft does not turn. Not a VC problem.
The electrical switch works fine. I disconnected it and the light stayed off.
This says the mechanism inside is moving to some degree, however it doesn't engage.
Today I will take the syncro off the stands and go for a drive. Maybe that is all that is needed...hopefully.
It has been on the stands for 3 months now during the full renovation and just maybe, the mechanism is a little stuck.

Will report back.

Peter


Peter,

Try taking off the two small vacuum lines and get a small air compressor (a cheapy as their flow is low) and put it on one side and see what turns after. Then try it on the other side.

I sorted my rear diff-lock issues this way and I could see my pin getting stuck in operation.

You may see something similar?

Cheers,

Skot

On 9/09/2015 10:27 AM, kestel.p@bigpond.com [Syncro_T3_Australia] wrote:

The drive shaft does not turn. Not a VC problem.

The electrical switch works fine. I disconnected it and the light stayed off.
This says the mechanism inside is moving to some degree, however it doesn't engage.
Today I will take the syncro off the stands and go for a drive. Maybe that is all that is needed...hopefully.
It has been on the stands for 3 months now during the full renovation and just maybe, the mechanism is a little stuck.

Will report back.

Peter

As i understand it there is a pin that is operated by the solenoide which toggles the operation of the decoupler, it will sometimes seize up you can manually check this via a pair of long nose pliers to see if it is free.
bob
 
Sent: Wednesday, September 09, 2015 10:27 AM
Subject: [Syncro_T3_Australia] Re: Decoupler Fault
 
 

The drive shaft does not turn. Not a VC problem.

The electrical switch works fine. I disconnected it and the light stayed off.
This says the mechanism inside is moving to some degree, however it doesn't engage.
Today I will take the syncro off the stands and go for a drive. Maybe that is all that is needed...hopefully.
It has been on the stands for 3 months now during the full renovation and just maybe, the mechanism is a little stuck.
 
Will report back.
 
Peter
hi ..
well naturally ..that is one of the 'features' of a Syncro's AWD system ..all 4 tires have to match nearly identically.
Very little margin there is my understanding ..for the health of the VC.

so advanatages to both versions of a default mode..
if it goes to 2WD tires don't have to match very much is one scenario.

on the other hand ..I was imagining being 'way out' somewhere really remote ..
in difficult driving situations ....say deep sand.
where not having AWD could be a real problem.

if the default was to AWD..
the worst that could happen is a person would have to remove the driveshaft to get 2WD, a simple nut and bolt operation ..if for some reason they had mismatching tires.

On 9/8/2015 1:56 PM, Scott Pitcher spbconsulting@bigpond.com [Syncro_T3_Australia] wrote:

Scott,

I would totally agree with that - unless you also had the issue of a tyre that was mismatched for some reason and you had to drive for a while before you could get a properly matching tyre. 4wd would damage the drive-train in that situation and 2wd would not.

But I would rather as you suggested - automatically revert to 4wd not 2wd.

Cheers,

Skot

On 9/09/2015 9:33 AM, 'SDF ( aka ;jim lahey' - Scott ) ' ScottDaniel@turbovans.com [Syncro_T3_Australia] wrote:

on could make sure proper vacuum is getting the decoupler vacuum connection.
..before digging deeper.

though one would think ..it the light on the dash says the right thing ..
the parts that move inside the decoupler housing to operate the light ...that should say it's working externally and moving that switch-affecting part inside.
At least it's not to hard to take the decoupler off the front of the trans.

I was surprised ..on the last one I installed anyway ....pretty sure it's like this :
the default ( like if vacuum isn't working ) position is 2WD ..thought that was weird.
I'd want the default 'swithching-mechanism-not-working' to be AWD.

so if it breaks ..you're back to AWD as original.

In my opinion many german automotive things are designed to work right only when they ARE right ..
I it's going to fail ..you'd want the decoupling ability to fail, automatically reverting to AWD.
Safety issue even.
Like get out of really bad boonies issue.


On 9/8/2015 2:04 AM, cathrich1@yahoo.com.au [Syncro_T3_Australia] wrote:

As Arne said, if the decoupler works the tail shaft will turn. I would also expect even a failed VC would drag enough to turn the front wheels when your up on a stands.

Does the light come on reliably when switching on/off? This would indicate the selector shaft is moving as it should and the vacuum unit and switch are also working. You could also take the switch out and confirm that is working and see the selector shaft moves also.

If the selector shaft is moving fine, then it indicates something is wrong further inside.


Silly question maybe, but I assume neither front wheel turns?


Richard




Peter when you test make sure you do some wide arc turns left and right on grass or loose surface as it helps the drive to engage due to the contesting ratios aligning due to the different arcs front and rear left and right wheels, might help ???

On Wed, Sep 9, 2015 at 10:27 AM, kestel.p@bigpond.com [Syncro_T3_Australia] <Syncro_T3_Australia@yahoogroups.com> wrote:

The drive shaft does not turn. Not a VC problem.

The electrical switch works fine. I disconnected it and the light stayed off.
This says the mechanism inside is moving to some degree, however it doesn't engage.
Today I will take the syncro off the stands and go for a drive. Maybe that is all that is needed...hopefully.
It has been on the stands for 3 months now during the full renovation and just maybe, the mechanism is a little stuck.

Will report back.

Peter


Don't forget there is not really a true default position for the diff lock/decoupler. The vacuum actuator at the diff lock or decupler is pulled in each direction with vacuum selected by the switch position.

If you think of all the likely failure modes, two common ones are a stuck actuator shaft or loss of vacuum (at the actuator), each of these failures will result in it failing in the position it was last at.


In the case of a stuck selector shaft, it's most likely to get stuck in the position it spends most of it's time (eg off), with a loss of vacuum, it depends on where the leak is, if it's on the "supply" line to your dash switch, it will fail where you were last, if it leaks between the dash switch and the actuator, it will not switch in the direction of the leak.   (I highlight "supply" as you don't supply vacuum, it just opens the selected line to vacuum from the engine)


If you wanted, you could also swap the vacuum lines at your actuator, this will swap which direction the actuator pulls in relation to the switch position. It doesn't achieve much as there is not really a default position, also this would get confusing though as your switch would be pulled out for 2WD and the light off.

In a break down situation you could just remove the vacuum actuator and manually put the selector shaft in the desired position (well not easily as you would need to align the drive dogs some how while pulling the selector)


Another interesting point to note is the addition of a reservoir and a check valve (between the engine and vacuum reservoir) in the system. Your engine manifold vacuum fluctuates depending on engine load, so if you left these two items out of the system, the vacuum at the actuator would also fluctuate during normal driving.

If you think of your system having a very minor leak, leave these two items out (check and res) and your driving under heavy load for a while (low engine vacuum) , if the system had a "default" position you risk this changing inadvertently.

I would consider the system safer as is rather than having a default position.


http://www.syncro.org/sitephotos/decouple.JPG


http://www.obsolyte.com/vanagon/VanagonProTraining/86Vanagon/040.jpg


Richard


It's working!
I took the syncro down the beach and gave her a good workout!
I guess the mechanism was a bit seized...