This all makes sense. 
Thanks to (almost) everyone for your input!

Cheers,
Matt

> On Oct 19, 2021, at 8:08 PM, Edward Maglott <emaglott3@gmail.com> wrote:
> 
> There's the why the axle is shifting in and out along its length. I never
> understood that part of it. That's also why you can't simulate the
> condition that occurs even if you deflect the suspension to the max in the
> shop. Because it's not under load.
> 
> My van would do this climbing mountain grades. Sometimes it would start
> out faint and slowly increase in intensity then fade out. If I swerved the
> van to cause the suspension to deflect with the body roll the sound did not
> change.
> 
> Edward
> 
>> On Tue, Oct 19, 2021, 8:51 PM vw_van_fan_Mark <madvws@cox.net> wrote:
>> 
>> One of the CVs has a bad wear spot or spots.
>> The deep pits occur in the spots where the balls spend the most time.
>> The balls dig into the surface of their tracks under under engine load.
>> Every time the axle rotates while at an angle the balls move back and
>> forth in their groves.
>> The greater the angle of the axle the farther the balls have to travel.
>> When you lifted the van you increased the travel distance of the balls
>> and now they have to move back and forth fully across the old pit(s)
>> where they used to spend more time.
>> Since they are traveling more distance in the same amount of time they
>> are also moving faster.
>> When under load the balls are forced firmly against their grooves as
>> they follow them.
>> When the ball encounters the wear pit it momentarily sticks but then
>> abruptly launches out of the pit.
>> This action causes the whole axle to jump sideways.
>> When the axle rotates but isn't under load the balls just glide over the
>> deep wear pits without getting momentarily caught in them.
>> 
>> Mark
>> 
>> Vanagon Man wrote:
>>> This all makes sense, especially since I put on the GW lift springs
>> recently.
>>> Except….
>>> 
>>> Why would it stop make the sound when I take my foot off the accelerator?
>>> 
>>> 
>>