At steps 7-9 it might be noted that it is a little
tricky removing the casing to get to the VC.  It can
hang up on the Diff. mount bar, the one in a "U" shape,
and I had to remove that bar to get it off and out of
the way.

Any one have the part numbers handy for the drive shaft
nuts that must be replaced?

I will be upgrading the syncro.org site soon and will
restore the photos for the VC change.  The site where i
had the photos stored went under.  Peter dug them up
for me and I can send them out till the site is fixed
again.   Maybe I can use this description on the site?

Steve

Derek Drew wrote:
>
> OK Brian. You are one of many people asking me for a
> definitive guide to replacing your VC. So for the
> benefit of the archives, here goes the best most
> current version of these instructions. No special
> tools or automotive experience are needed for this
> job, and because it is so simple, it should not be
> farmed out to a transmission shop. The best thing I
> could say, going from memory, is to....
>
> 1. Drive van up on 4 ramps
> 2. Put jackstands under van in case ramps fail
> 3. Record and mark the alignment of the driveshaft to
> the front differential so that you can put the same
> bolt through the same holes of each unit upon
> reassembly. This will reduce the chances of your
> ending up with an out of balance driveshaft on
> reassembly.
> 3. Unbolt the four forward bolts holding the
> driveshaft on with either a 1/2 inch or 13mm open end
> wrench and some liquid wrench. If the 13mm wrench
> doesn't work that great, try the 1/2 inch open end
> wrench.
> 4. Loosen the bolts holding the front differential so
> that differential may be shifted around.
> 5. Shift the front diff forward so that the
> driveshaft will fall away from the front diff. Shift
> that driveshaft out of the way.
> 6. Remove the oil from the front diff through the oil
> drain hole. Throw that oil away by bringing it to
> your nearest auto repair shop for disposal.
> 7. Remove the 13ish? 13?mm bolts holding the back
> half of the front differential onto the vehicle and
> then pop the rear third of the differential off
> backwards. Do not looosen the big bolt at the
> rearmost point in the front differential
> 8. Have something on the ground to catch the residual
> oil that will spill out.
> 9. Pull the VC out and replace, being careful to
> reinstall the little metal washer that is wedged in
> there. No special tools or measurements of any kind
> are needed.
> 10. Bolt everything back together, but bolt the front
> differential down last after shifting it around to
> properly seat it in relation to the rear
> transmission. When bolting the driveshaft back on,
> either replace the 4 driveshaft nuts with factory new
> ones the way VW says to do it (proper way), or just
> use Red Loctite the way about half the people on the
> list do it (universal list method) or reuse the
> original nuts with no loctitie the way the other half
> does it (pogo stick method; see below).
> 11. Refill the front differential with GL-5
> Transmission oil using the factory specified
> viscocity. Mobil 1 makes a good GL-5 for the front
> diff. (Make sure not to use GL-5 in the rear
> transmission, however, as that takes only
> GL-4--eveybody wisely uses Redline GL-4 synthetic for
> the rear.)
> 12. The entire job should take you about 1 hour. But
> for some reason --I cannot predict in advance why --
> it will actually take you 5 hours :-). Some members
> have reported broken bolts holding the diff in place,
> or broken rubber mounts, so be prepared to hunt these
> parts down if you decide you need to replace them.
> 13. Some people decide to remove the diff entirely to
> do this job. You can do that, but that means you have
> to disconnect the front CV joints, which is a pain.
> Still, those front CV joints probably need their
> grease to be renewed anyway. And as long as you are
> regreasing the inner front cv  joints, you might as
> well do the outers too, and inspect the boots, and
> then why not the rears and HEY lets not loose focus
> here...
> 14. The best description on how to change your VC was
> originally posted to the list by Rainer about three
> years ago, but Steve Schwenks photo essay matched
> this post in utility and interest. Too bad it is not
> on syncro.org right now.  I will copy Ranier's post
> below.
> ABOUT THE POGO STICK METHOD.
> This is actually a method of easily removing the
> transmission and engine from the vehicle.
> Essentially, the procedure is to skip using loctite
> on the nuts that hold the driveshaft on the front
> diff, and don't replace those nuts with new nuts
> either. Just reuse your old nuts even though the
> factory says to replace them. When the nuts or bolts
> eventually fail, the driveshaft will drop down on the
> highway and get lodged on a rock, crack, or other
> obstacle and remove your trannsmission and engine in
> about two seconds. This also works in the event of a
> front U-joint failure. If this does not appeal to
> you, install a strap that holds up the front
> driveshaft in the event its front attachment point
> fails. I haven't put my strap in yet myself, but I
> think about it from time to time.
>
> >> There is an excellent article by Steve on how to
> >> replace the VC at www.syncro.org in the Tech
> >> section called "Replacing the VC (photos):
> >
>
> Reproduced below is Rainer's version of the above. It
> differs from my version in some important respects so
> it pays to read both posts. Note that Rainer is one
> of the world's leading observers of the Syncro
> Viscous Coupling, and is of much higher intellect
> than the average Vanagon or Syncro poster so we are
> lucky to have him among us.
>
> > VW's original (German) repair manual doesn't say
> > much  about how to test
> > the viscous coupling.  They only recommend placing
> > the  rear wheels in a
> > break testing stand.  If you then switch to  the
> > G-gear (creeping gear),
> > the front  wheels should move the van  out of the
> > test stand as soon as
> > the engine is revving slightly above idle.   If the
> > front wheels fail to
> > do so the viscous coupling is to be replaced, VW
> > says.  VW adds another
> > tiny sentence  to this, saying that only  when the
> > engine  is revving at
> > idle and with the G-gear  switched in, the viscous
> > coupling is able  to
> > absorb all the torque to the front wheels and keep
> > them from moving.
> >
> > To me  this   last and  rather   ill-formulated (in
> > the  German  manual)
> > sentence is the key to testing the viscous
> > coupling.   For in most cases
> > we  are not dealing with viscous  couplings doing
> > less than their share,
> > but rather with hard-going viscous couplings  which
> > don't have a problem
> > at all in  moving the van  out  of the  test stand
> > with  the engine just
> > idling.
> >
> > Thus the really important thing here is not the van
> > successfully leaving
> > the test stand.  On the  contrary, the important
> > thing  here is the  van
> > not moving and staying put in the test stand with
> > the G-gear switched in
> > and the engine just idling.  If your  Syncro
> > doesn't pass this test your
> > viscous coupling is probably  worn out and  ready
> > for a replacement.  Or
> > put  the other way  round: as  long  as your van's
> > viscous  coupling is
> > working properly you will not notice your van has
> > got one.
> >
> > As   soon as   you are encountering   problems
> > with your Syncro   when
> > cornering, in particular after a long and  fast
> > drive, or  as soon as --
> > despite  of power  steering --  steering becomes
> > a  bit difficult when
> > turning and the Syncro slows down considerably when
> > going round a corner
> > ... as soon as one or  more of these  things are
> > happening, your viscous
> > coupling is most  probably due  for  replacement.
> > When  the tires start
> > whining while cornering it might well be too late
> > already ...
> >
> > I once had all of these symptoms and it was
> > immediately clear to me that
> > the viscous coupling was  the culprit.  But it
> > took  some time for me to
> > react, and it took some more time for the new
> > viscous coupling to arrive
> > at my door.  Should you ever encounter similar
> > problems I would urge you
> > to  immediately get under  your van and  remove
> > the drive shaft between
> > gearbox and front  diff.   If you  fail to do
> > this  and wait  too long,
> > severe damage to the  gearbox and/or front  diff is
> > the probable result.
> > Removing the drive shaft is pretty straight
> > forward, just four bolts and
> > nuts (13  mm) on either   end of the  drive
> > shaft.   Then loosen  (just
> > loosen, don't remove  them) the three nuts and
> > bolts (17 mm) which hold
> > the front diff in place, so the front diff can move
> > out of the way a bit
> > for the drive shaft to be removable.   Don't forget
> > to again tighten the
> > 17 mm screws.
> >
> > When   I  was shopping  for  a new  viscous
> > coupling  (according to all
> > reliable sources  I contacted they cannot  be
> > repaired)  I asked several
> > knowledgable people how long   a viscous coupling
> > is expected  to last.
> > Apart from "it depends"  (an employee at
> > Steyr-Daimler-Puch  in Austria,
> > the firm which  was producing the Syncros  and in
> > particular the viscous
> > couplings for  VW) the answers ranged from  "some
> > 60,000 km" to "between
> > 170,000  and  200,000 km".   Mine  was replaced
> > after  150,000 km but I
> > bought the Syncro with  80,000 km on the   tach and
> > don't know  for sure
> > whether  or not this  was still  the  first
> > viscous coupling.   But I'm
> > assuming it was.
> >
> > As for the  reason  why the silicone  in  the
> > viscous coupling  gets too
> > stiff and   starts  causing trouble   the people
> > I asked  unanimously
> > answered: to much strain.  However,  this is not
> > referring to relentless
> > off  road driving in  groundless mud, but rather
> > to small but permanent
> > differences in rotational speed between front and
> > rear axle while doing
> > normal on road  driving.  These differences  in
> > rotational  speed can be
> > caused by  such things as unequal  tire wear or
> > different tire pressure.
> > Tire diameters should be the same within a 2 to  4
> > mm tolerance.  Or, in
> > other words,  if you're measuring  the depths  of
> > the grooves in  your
> > tires, the differences should not exceed 1 to 2 mm.
> >
> > Thus  people not caring  tire   pressure and  tire
> > wear,  people  having
> > mounted different  tire brands on the front  and
> > rear axles,  as well as
> > people never routinely  using their spare tire so
> > it gets  worn roughly
> > the same way as the other tires are most  probably
> > ruining their viscous
> > coupling pretty fast.
> >
> > Removing the drive shaft as an emergency measure:
> > If you  have  to, and provided  you're  slim
> > enough, you  can remove the
> > drive  shaft on the  bare ground (at least if
> > it's  a Syncro 16"), just
> > with a little help  of the  factory  jack.  In case
> > your  driveshaft was
> > balanced  in its current position,   it may be a
> > good  idea to mark the
> > alignment points of the flanges before removal.
> > Then you'll have to use
> > a pair of 13mm wrenches (due to space constraints
> > only open wrenches are
> > usable) to remove four bolts and  nuts at either
> > end  of the drive shaft
> > (sometimes the  nuts are  only  12mm).  If you
> > want  to do it  properly
> > you'll also have to loosen (only loosen,  don't
> > remove!)  the three nuts
> > and bolts (17 mm) which hold the  front diff in
> > place via rubber stops,
> > so the front diff can move out  of the way a  bit
> > for the drive shaft to
> > be removable.  However, when lying on the bare
> > ground just below the van
> > this might be  hard to  do.  If your  drive  shaft
> > has got  this  rubber
> > element in it  you may try  to simply use  a screw
> > driver  to cautiously
> > separate the two flanges at one end of the drive
> > shaft.  Knocking gently
> > at the flanges at the other end will then take the
> > drive shaft down.  As
> > to the rubber element: in diesel engined and FI
> > vans the rubber element
> > was facing   opposite sides.  Thus you'd   better
> > take some  notes as to
> > whether  the rubber element is at  the gearbox end
> > or  at the front diff
> > end.
> >
> > Replacing the viscous coupling:
> > To replace  the  viscous    coupling you'll  have
> > to pull   the  front
> > differential first.  I don't think it's feasible
> > to replace the viscous
> > coupling right  under the van with the  front
> > differential in place.
>
> Derek's Note:
> Californians on the list proved otherwise so if you
> want to leave the diff in there go ahead. Sam Walters
> did it on the ground, but he indicated it was a pain.
>
> > In
> > particular, reassembly would thus be much more
> > difficult and would cause
> > plenty of cursing.  And you'd have to drain the oil
> > first.  By and large
> > there is  no  witchcraft involved in  pulling  the
> > front  diff,  but you
> > should do it  with the van on a  lifting platform
> > or above a grease-pit.
> > And it takes two people as well as a floor-jack.
> >
> > First of  all losen but   don't yet remove the
> > three 17mm nuts already
> > mentioned which hold the front diff in  place.
> > Then remove  the speedo
> > cable  as well as the six  screws in each of  the
> > inner CV-joints.  For
> > this  screws you'll need  either a   6mm hexagonal
> > or an 8mm multipoint
> > socket.  If  you haven't done  it yet  you should
> > now  remove the  drive
> > shaft as   described above.   If   you have  a
> > front  diff  lock (never
> > officially exported  to  the  US) unplug   it
> > electrically as  well  as
> > pneumatically   (tag the pipes so  you  can't
> > confuse  them later).  Now
> > remove the  screw holding  the vent pipe  of the
> > differential  and then
> > remove the  three 17mm nuts  and bolts holding the
> > front diff.  Get the
> > floor-jack   in place and remove the   front and
> > rear mounting brackets.
> > Then  together with a   second person cautiously
> > move  the diff forward
> > along the skid plate and  out.  Look out for the
> > diff lock if there  is
> > one.
> >
> > Place the front diff on your workbench in such a
> > way that the flange for
> > the  drive shaft is facing  upwards.  You can now
> > easily remove the ten
> > 13mm bolts with which the housing of the viscous
> > coupling is attached to
> > the front diff without risking any  oil leaking.
> > Lift the housing which
> > is  containing the input shaft.  You  will  now see
> > the viscous coupling
> > itself  and a little spacing   collar sitting on
> > top  of it.  Take this
> > spacing collar, grease the top rim of it and again
> > place it on the input
> > shaft in the housing and slightly press  it with
> > its greased rim against
> > the bearing so it will stay there.  This  will
> > greatly ease reassembling
> > the diff later.  Now remove the old viscous
> > coupling  and put in the new
> > one.  Then apply silicone sealing compound to the
> > contact flange of the
> > housing  and, inserting the input  shaft into the
> > viscous coupling, put
> > the housing back in place.   Finally, gently
> > tighten  the ten 13mm bolts
> > crosswise, applying 20 Nm (15  ft lb.), and your
> > front  diff is ready to
> > be reinstalled.
> >
> > Perhaps you  should use the opportunity while  the
> > diff is still sitting
> > on your workbench to  check what has been caught
> > by the magnet at  the
> > oil drain plug.
> >
> > To reinstall the front diff in the van simply
> > reverse the steps laid out
> > above,  at the very  last  fastening the screws
> > of  the front and  rear
> > mounting brackets as  well as the  three  17mm
> > bolts through the  rubber
> > stops (apply 45 Nm (33 ft lb.) to these).
> >
> > Tools and torques needed:
> >
> > Installation of the front diff:
> >    17mm socket and ratchet, perhaps with
> > extension.  Use 17mm wrench to
> >    counter at the other side, 45 Nm (33 ft lb.)
> > VC housing:
> >    13mm socket with extension and ratchet, 20 Nm
> > (15 ft lb.)
> > CV-joints:
> >    either 6mm  hexagonal  or 8mm  multipoint
> > socket  with extension  and
> >    ratchet, 35 Nm (26 ft lb.)
> > Drive shaft:
> >    Two open 13mm wrenches (sometimes only 12mm for
> > the nuts), 35 Nm (26
> >    ft lb.)
> > Acknowledgements:
> > Special thanks go to Wolfgang Carolsfeld in Canada
> > <wolfgang@island.net>
> > who not only proofread this text, helped  me with
> > some technical English
> > terms I failed  to find in my  dictionary, and did
> > the math involved in
> > converting  the torques  from Nm  to  ft lb,  but
> > who also successfully
> > applied the underlying German version of this text
> > to his Syncro to make
> > sure it works :-)
> > ------------------
> > ---------------------------------------------------
> > | Rainer M Woitok                  | Phone:
> > (+49-9131) 85-27811,-27031 |
> > | Regionales Rechenzentrum
> > |                                   |
> > | Friedrich-Alexander-Universitaet | Fax  :
> > (+49-9131) 30 29 41        |
> > | Martens-Strasse 1                | Telex: d 629
> > 755 tf erl           |
> > | D-91058 Erlangen
> > |                                   |
> > | Germany                          | Mail:
> > Woitok@RRZE.Uni-Erlangen.DE |
> >  --------------------------
> > -------------------------------------------