Hmmm, that could be it.

  I did replace the one side mount just a month or so ago when I changed to
the 2.0 liter motor.  But the clearance is a little tight now at the
head/intake...Seems weird the sound would remain essentially unchanged,
considering all the changes to the motor and a completely different exhaust
system, hung very differently.
  But that possible cause does seem to fit the sound under a heavy load
symptoms....Seems like I would have noticed during my  recent time spent
under, changing all that mounting and stuff...but then I did miss the pilot
bearing...so I am not all that observant.  I shall spend some time looking
with that in mind...maybe put a lever onto the motor and tilt it like it
should do when under a big load..
  Thanks, guys.
  Don Hanson

On Fri, Jan 14, 2011 at 2:56 PM, Scott Daniel - Turbovans <
scottdaniel@turbovans.com> wrote:

> is the engine torque-ing over under heavy load only , and allowing say,
> part of the exhaust system ..
> or some other part , to contact the frame of the van  ?  and thus transmit
> engine vibration directly to frame/body briefly .
>
> I had one inline four cylinder engine car once..
> an exhaust shop...doing dorkey work as they often do....mounted the tail
> pipe so there was just one rubber gromet around a large sheet metal screw
> thing...like lag bolt almost ..
> right at 3,900 to 4,100 rpm , regardless of load in this one ..it would
> buzz like crazy.
>
> inline fours usually have a narrow buzzy period around 70 % of max rpm .
> though yours sounds more load related..
> as though the engine was torueing over and allowing something to hit.
>
> scott
> www.turbovans.com
>
>
> ----- Original Message ----- From: "Don Hanson" <dhanson928@GMAIL.COM>
> To: <vanagon@GERRY.VANAGON.COM>
> Sent: Friday, January 14, 2011 10:13 AM
> Subject: Odd sound from rear end...(not Friday and no smart 'subject'
> remarks please)
>
>
>
>   I have an 84 with a 5sp diesel tranny and an inline VW gas motor..have
>> had
>> for about 3 yrs now..with this sound coming from the drive line,
>> occasionally,  ever since I got the van...I have done a lot of work
>> involving the driveline during my ownership.  I still hear this sound
>> every
>> so often, without any perceivable change in the way it presents itself or
>> in
>> the sound itself...at least nothing I can detect.  Here's what happens...
>>
>>  When I have let the clutch out totally and then accelerate strongly or
>> accelerate up a steep pitch from a slow slow speed, in either 1st gear (a
>> semi crawler gear that I rarely use) or in my second gear (my normal
>> starting gear)  I get a sound like when you drive over a grated bridge
>> deck,
>> or  a vibration like when you encounter those sound strips they sometimes
>> inscribe in some highways...  Kind of a gnarly buzzy sound that only comes
>> with a big load at low speeds and low RPMs...So if I punch it in 2nd gear
>> at
>> 15+ mph...smooth acceleration only...But if I am on a sharp incline and
>> going say..2-5mph and hit it,  I get that 'bridge-deck buzz' until I gain
>> speed or lessen the acceleration.  It does not seem to be
>> clutch-related...It happens after the clutch is fully engaged, or even if
>> I
>> decelerate in gear without using the clutch and then give it the pedal...
>>
>>  I recently replaced my engine, new clutch, throw out bearing, pilot
>> bearing and had the inner CV joints out a couple of times.  They looked
>> good
>> with plenty of grease and no damage to the boots.   The sound did not
>> change
>> after having all that apart' multiple times.  I did check and re-grease
>> the
>> outer CV joints about 2 yrs ago, but I have not had those apart since..At
>> that time, they looked OK, however, I have no real way to judge that other
>> than what I have read.
>>
>>  I am thinking maybe I should simply do a couple of those axle/cv kits and
>> see if that stops that noise...which I suspect might be the outer CV
>> joints.
>>
>> I am thinking 'not tranny' because the sound is unaltered by gear
>> selection
>> and there are no alarming sounds nor did anything bad come out during any
>> of
>> my tranny fluid changes. No problems with gear changes, either.
>>
>>  Do my outer CV joints have the capacity to cause this sound?  Am I on the
>> right track, do you think?  Thanks in advance..
>>
>>  Don Hanson
>>
>
>