Date:         Sun, 31 Mar 96 22:02 CST
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         khooper@wsp1.wspice.com (Ken Hooper)
Subject:      68: What is this damnable noise???


Some experienced person please help with this. It's about to drive me bonkers:

This noise is new. It showed up all at once.

The noise is low-frequency and it reverberates throughout the bus. I can't
tell where it's coming from, it depends which way I turn my head.  The
noise begins precisely at 43 miles per hour, and increases in frequency and
volume the faster the bus goes. It doesn't grind; it's somewhere between a
hum and a sustained moan. There is a vibration to it but the vibration is
tactile, not aural; you can only feel it.

If this noise was coming from a musical instrument, it would be a double
bass playing a sustained note with a bow. Midrange (for a bass). It's a bit
like riding in a large passenger aircraft and sitting on the wing, but
without the whine and whistle. Get it? Like a low, smooth, sustained
head-buzz. Though it sounds *very* much like a sympathetic vibration, it
does not throb at any speed, nor does it disappear at any speed above 43.

The noise disappears entirely when the bus is taking curves. It only
happens on straights.

The noise does not care a bit about engine speed. Doesn't matter whether
I'm in fourth or third. But I can make it cycle with the accelerator,
putting it under load and backing off. It's much louder under load.

I replaced the right rear wheel bearings. If I had to guess, I'd say it's
coming from the rear, and the right wheel had lots of play in it. Lovely
new FAG bearings and seals with lots of slippery grease. Took five hours.
The noise perseveres.

The CVs seem fine. Boots tight, no clicking in corners.

Today I had the trans oil changed. I do believe this trans is elderly; the
syncros are balky and it has its bitching and moaning routine that it must
do when warming up. But it has never yet popped out of gear. Changing the
lube made no difference in the noise whatsoever. The old oil was not low,
there was plenty of it. No chunks came out that I could see. No shavings
stuck to the plug.

The day before the noise came to town, I had adjusted all the brake shoes
and the parking brake. The cables are old and slack and I could not
possibly have locked the parking brake on even if I didn't know what I was
doing. None of the shoes are locked on. None of the hubs are hot when I
stop. Transmission isn't hot, either.

There is no reason to believe that it is main bearings. This engine is
reputed to be nearly new, there are no oil pressure problems, the bus uses
no oil and has no leaks at all. Good power, good mileage, no smoke. Just
passed emissions.

There are no symptoms other than aural ones (and no jokes from the
vanagon@lenti wags)(as if I expected that to stop you) and the dimly-felt
vibration. But this noise is *loud*.

This has got to be somewhere between the front of the cranshaft and the
tire rubber. What in the hell is it?

--Ken
  '71 Bus, '68 Westy