I purchased a Welty with a "bad auto tranny" a few years ago.  Turned out to be a catastrophic failure of the cv joint - the cage broke.  I suspect it knocked for a long time and then finally gave out.

So yes, it can definitely happen...

Sent from my iPad

On Jan 3, 2013, at 16:44, Mike B <mbucchino@CHARTER.NET> wrote:

>  Well, one time I had a rear inner CVJ on my '84 Vanagon GL come
> loose, which amounted to catastrophic failure while I was driving.  a
> couple of the CV bolts somehow came loose, and the remaining ones
> snapped off flush in the flange.  I could not drive any further, so I
> put it back together with the 2 good bolts and carefully drove home.
> VW's have always amazed me with the ability to still get them home after
> some sort of problem.  There was very little warning or noise before
> that issue happened.  This particular van had over 200K miles and had
> many repairs completed over a period of several years while I owned and
> maintained it.  I only sold it when I found the '87 Westy GL that I'm
> driving now, to make room in my driveway.  I guess you never know...
> 
> Mike B.
> 
> On 1/3/2013 6:17 PM, Craig Cowan wrote:
>> I've never heard of a rear cv on a vanagon failing catastrophically enough
>> to affect driving.
>> Generally they just start to clunk when turning one way.
>> 
>> Yep, 1 wheel drive in snow. GOOD snow tires help alot.
>> Otherwise a 2wd vanagon is "ehh" in snow.
>> 
>> The droning could also be a transmission related issue, such as a failing
>> Ring/Pinion Gear or Bearing.
>> Rule out wheel bearings first and change your transmission fluid if you
>> never have.
>> 
>> -Craig
>> 
>> 
>> On Thu, Jan 3, 2013 at 5:59 PM, Zoran Mladen <zmaninco@yahoo.com> wrote:
>> 
>>> I would agree that the droning is likely a wheel bearing.
>>> 
>>> As far as the one wheel drive...that is correct!  These vans...as most
>>> cars are...is a one wheel drive vehicle.  Whichever rear wheel has the
>>> lesser resistance will spin.  Hence, if you raise one rear wheel in the
>>> air, the van is not going anywhere.
>>> 
>>> Sent from my iPad
>>> 
>>> On Jan 3, 2013, at 15:35, Ed Duntz <eduntz@HOTMAIL.COM> wrote:
>>> 
>>>> As soon as it's not quite so cold out, I'll jack up the van and do a
>>> little more investigating, but until then, I pose this question here. This
>>> is about my 1984 Vanagon.
>>>> I have two symptoms. One is a noise from the rear which I think might
>>> best be described as a "droning." I hear it almost all the time that the
>>> vehicle is in motion. I haven't really listened for it at low speeds, but I
>>> hear it when I'm going about 30 mph, my average speed on my back roads. It
>>> is more prominent when cornering to the left. I hear it whether the van is
>>> in gear or not, and whether the clutch is in or out. This is what makes me
>>> think it may be a wheel bearing.
>>>> My second symptom makes me wonder if I have a cv joint issue. I realize
>>> that when a cv joint goes, it usually means that the vehicle won't move, as
>>> the transmission can't turn one axle if the other has a bad cv. But I was
>>> traveling on snow, and I wonder if that allowed the wheels to turn
>>> independently and made a difference. I was traveling up a slight incline on
>>> snow and the van went up the hill partially sideways, probably at a 30
>>> degree angle. It seemed like one wheel was turning more than the other, and
>>> I had to steer accordingly so that the van went up the hill in my lane, but
>>> at an angle. There was not significant difference in the rear tires to make
>>> me think that had a large impact.
>>>> Any thoughts are appreciated.
>>>> 
>>>> Thanks,
>>>> Ed