two points to offer :
to answer the original poster's question......yes, the drive shaft always
turns any time the front tires are turning.
Solid connection there from front wheels, through the front axles, and the
front differential, to the drive shaft.....
all connected together, so they are always turning anytime the front wheels
are turning.

the common way to test for a bearing rumble is to gently swerve left and
right at about 35 mph.
If the sound level of the rumble changes with direction of the swerve......
say it's quieter swerving right, and noisier swerving left, you would
conclude that a right side wheel bearing is the cause.
*not always* but the majority of the time.......
the 'quite side' is the side with the bad wheel bearing/s .......as there is
less load on the right side when swerving right, although I did get tripped
up on a front wheel drive car once......it was front bearings on the noisier
side, not the quieter side
as would be normal and common.,

Scott
www.turbovans.com

----- Original Message -----
From: "Jim Johnston" <inmytree1@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, March 24, 2009 4:41 AM
Subject: Re: Rumble

> Not sure about your syncro, but in my plain ol' GL, rumbling was caused by
> a
> bad wheel bearing...
>
>
>
> On Mon, Mar 23, 2009 at 9:55 PM, Mike Miller <mwmiller@cwnet.com> wrote:
>
>> VAN Folks,
>>
>> At certain speeds, 45-65 MPH, there is a distinct rumble to be heard on
>> almost all road surfaces [some road surfaces are so noisy they drown out
>> other noises].
>>
>> Weird thing is it can only be heard from the drivers seat, not the
>> passengers.
>>
>> 87 syncro with a decoupler. I've only tried it decoupled. I suppose I
>> should
>> couple it up and check that too.
>>
>> Does the front drive shaft rotate even when decoupled, driven by the
>> front
>> wheels?
>>
>> Mike
>>
>
>
>
> --
> Jim
> Wilmington, NC