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