VC versus Permanent 4WD

1
Thanks Joachim for your very informative reply to my question. Very
nice to wake up to news direct from the horses mouth so as to speak
(i.e Germany; the home of our much loved syncro's.) I teach at a
college and if half my students had your command and confidence at
English I'd be more than happy. Do permanent 4WD drive shaft syncro's
have front and rear diff locks like the viscous coupling syncro's? Are
their 4WD capabilities as good as a VC syncro with diff locks, or do
they (permanent drive shaft syncro's) manage just as well without diff
locks?
Are the permananent drive shaft syncros only good for sand. What about
mud, steep terrain, boulders and river beds,snow and gravel/dirt
tracks and fire trails.Can you drive on any of these in 4WD.
Also is it true that you cannot engage 4WD on the fly in non VC
Syncros; you have to stop before engaging.
Phil are you saying that permanent drive shaft syncro's always engage
in 4WD in the 'G' and reverse gear or did you mean the VC syncro's.
Many thanks everyone.
Michael
2
Michael,
 
At the risk of driving Ken to new heights of hyperbole, the dividing line between solid shaft and VC is the nature of the terrain. 
 
There was a post from Stuart regarding sand driving.  Hark to Stuart, because he is a dedicated diver and spends a lot of time traversing beach sand.  A solid shaft provides constant drive to the front diff with no lag, such as can be experienced with a VC, and has a demonstrable history of coping with most sand far better than a VC Syncro.  You can use front a rear diff locks with a solid shaft.  A solid shaft is also advantageous on very rough tracks, including rocks, with and without diff locks. Engaging the diff locks is dictated by the terrain facing you;  you select what is appropriate for the conditions.  Engaging the decoupler on the trot will destroy the coupling mechanism in the front casing of the gearbox, a very expensive failure.
 
You CAN'T use a solid shaft on any solid, grippy surface, because both axles will be driven at the same speed, no matter what.  This will destroy the drive line very quickly and VERY expensively.
 
As designed by Styer Puch, the VC system in the Syncro is an extremely good compromise, one which caters for a very wide variety of conditions and one which will get you through most situations.  The solid shaft caters for one extreme of usage only and does not cater for the other 90% at all.  Someone like Stuart will benefit greatly from a solid shaft because of the amount of driving he does on beach sand.  Someone who spends all of their time on next to impassable bush tracks will similarly benefit.  For the rest of us, the VC is that very wide reaching compromise that does most things very well indeed.
 
Les Harris
 
 
 
----- Original Message -----
From: evm614
Sent: Tuesday, May 22, 2007 5:29 PM
Subject: [Syncro_T3_Australia] VC versus Permanent 4WD

Thanks Joachim for your very informative reply to my question. Very
nice to wake up to news direct from the horses mouth so as to speak
(i.e Germany; the home of our much loved syncro's.) I teach at a
college and if half my students had your command and confidence at
English I'd be more than happy. Do permanent 4WD drive shaft syncro's
have front and rear diff locks like the viscous coupling syncro's? Are
their 4WD capabilities as good as a VC syncro with diff locks, or do
they (permanent drive shaft syncro's) manage just as well without diff
locks?
Are the permananent drive shaft syncros only good for sand. What about
mud, steep terrain, boulders and river beds,snow and gravel/dirt
tracks and fire trails.Can you drive on any of these in 4WD.
Also is it true that you cannot engage 4WD on the fly in non VC
Syncros; you have to stop before engaging.
Phil are you saying that permanent drive shaft syncro's always engage
in 4WD in the 'G' and reverse gear or did you mean the VC syncro's.
Many thanks everyone.
Michael

3
Hi,

just to answer you some questions:

If you are installing a "permanent 4WD" (in fact it isn´t, cause you
should never ever use this 4WD-mode on asphalt) you are just
replacing the VC in the front-gearbox with a bush, which also fits to
the gearing of the driveshafts.
To lock or unlock the 4 WD-mode you have to install some additional
parts at the rear gearbox.

But coming back to driving:

You can use this permanent 4 WD (which correctly means, that you do
not have a center-diff; the VC normaly acts as that) on every
slipping underground. There is no difference if you are driving on
mud, sand, slipping gras, rocks, gravels etc. JUst be carefull using
it on slip-proof underground, such as asphalt, cause you dont have a
center-diff which corrects different turning-speeds of the front and
rear-axle.

Compared to a working (!!!) VC i realy don´t see an advantage, except
you are playing in deep flowing sand. There the VC has the problem,
that it needs a turning-difference of the axles to transmit torque
from the rear to the front.

If you have some more questions, just feel free to write a mail to
myself...

Cheers,

Dirk
4
Michael,

"from the horses mouth..." I love this expressions, more please =;-)

Some of your thoughts have already been answered by Les.

Some of the rest would be:

Not all solid shaft syncros have both lockers necessarilly.

When we bought the solid shaft in 2004 we were recommended to engage
4WD only when going slow - meaning any speed around or below 40
km/h. It can be engaged/disengad while standing still and at ANY
speed with the COUPLING PRESSED AND ACCELERATOR RELEASED UNTIL 4WD
is ENGAGED/DISENGAGED. We have been doing this since more than two
years and 20.000 km now having no trouble or damages. We've even
engaged/disengaged it several times at speeds around 90 to 100 km/h
on the highway while doing more than 300 continous km's in heavy
rainy conditions.

I would NEVER engage a solid shaft in G or reverse when having to
drive a sharp corner due to the enormous stress put on the box.

Thanx

Joachim


--- In Syncro_T3_Australia@yahoogroups.com, "evm614" <mrphoto@...>
wrote:
>
> Thanks Joachim for your very informative reply to my question. Very
> nice to wake up to news direct from the horses mouth so as to speak
> (i.e Germany; the home of our much loved syncro's.) I teach at a
> college and if half my students had your command and confidence at
> English I'd be more than happy. Do permanent 4WD drive shaft
syncro's
> have front and rear diff locks like the viscous coupling syncro's?
Are
> their 4WD capabilities as good as a VC syncro with diff locks, or
do
> they (permanent drive shaft syncro's) manage just as well without
diff
> locks?
> Are the permananent drive shaft syncros only good for sand. What
about
> mud, steep terrain, boulders and river beds,snow and gravel/dirt
> tracks and fire trails.Can you drive on any of these in 4WD.
> Also is it true that you cannot engage 4WD on the fly in non VC
> Syncros; you have to stop before engaging.
> Phil are you saying that permanent drive shaft syncro's always
engage
> in 4WD in the 'G' and reverse gear or did you mean the VC syncro's.
> Many thanks everyone.
> Michael
>
5
.
> Phil are you saying that permanent drive shaft syncro's always engage
> in 4WD in the 'G' and reverse gear or did you mean the VC syncro's.
>

The decoupler is activated by the switch on the dash which pulls on a bowden cable which operates a vacuum valve on the gearbox. Or when you put it in G or Reverse, it operates the vacuum valve to the decoupler. So it was automatic to engage 4WD everytime in G or Reverse.

There are diagrams on the Syncro T3 Australia website.

The decoupler was only ever fitted with the solid shaft.

Phill