Late Bus Inexplicable Muffler Rattle?

[Amskeptic]

I had a rattling muffler that I was pretty sure was because it was loose in its saddle. Stuck a big thick washer between the retaining strap and muffler wall and all was secure . . . but the rattle was still there, most noticeable at idle. This repair will have broad applicability to any of the can type mufflers that showed up in 1975.

Upon closer investigation, I discovered that the tailpipe/flange/outlet stage pipe inside the muffler (see red in illustration) was causing this rattle, and stress fractures were showing up on the endcap from that undesireable motion. The pipes must be press-fit in the internal baffles or sumpin' and one tailpipe curb strike can be the beginning of the total destruction of your nice Leistritz muffler:

Loosened the retaining strap, shunted it aside, and started drilling successively larger holes in my nice OEM VW Leistritz muffler:

At 11/64"s or whatever, my nice fine-thread screw in my extra screws supply bag self tapped effortlessly into the wall of the muffler and reached the pipe inside and quieted the rattle right down. Unscrewed it, blobbed the hole with catalytic converter safe Permatex HiTemp RTV, and sent it home:

Note here that the screw is not visible underneath the retainer strap, and will never fall out besides . . . nobody needs to know that you are drilling holes in your nice OEM Leistritz muffler. Bonus, didn't need that big washer anymore to keep the muffler secure in the saddle. It is a pleasure not to hear that racket riccocheting off of walls anymore.
Colin:

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www.itinerant-air-cooled.com

[SGKent]

awesome. Mail me one of those screws and I'll send another Mexican meal coupon next time you are here.

Steve
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[raygreenwood]

There is a similar internal fracture based rattle of the other earlier type 4 bus/411 type muffler that is common as well.....sadly there is no way to fix it. Ray

[Hoody]

Thanks for the write up Colin. Very few of us with 75-78's still have the stock set up. I always wondered what was on the inside of a Leistritz. If you start selling your book or just "How to do this the Itinerant way" I will be first in line. I think Mr. Hoover has passed the torch.

[Ritter]

I can't believe you didn't repaint the strap.
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1978 westy 2L FI (needs a little bit less work)

[BusterBrown]

Excellent detective work and write up. From someone who still has his stock '78 exhaust and muffler, thanks so much for that!

I hate rattling noises, unless it's from a rattlesnake (which has saved me stepping on many a snake).

Now if I could just locate and fix those other rattles...
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1978 Sage Green Westfalia (Happy Trails, SOLD)
1977 Transporter

Life is short. Can I have some of yours?

[Westfabulous]

Good stuff Colin. I just tossed my original OEM Leistritz muffler as it finally rotted through on the bottom. It was sad to see it go, as it had the original date stamp going back 30 years. I bought an OEM muffler that looks the same, but is made in Israel, and isn't an OEM Leistritz. Just curious, when you tap into the muffler, do you snug the screw up against the internal pipe to reduce vibration, or did you sink it into the internal pipe? Wonder if my new OEM-ish muffler is the same construction inside?
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"I will gladly pay you Tuesday for a hamburger today."

[Desertbusman]

My new dual Thunderbird quiet (a joke) pack needed better paint so I lightly sandblasted the original stuff off. For the blasting it was laying on the ground in my yard. But the yard is small round river rock desert landscaped. And a couple small rocks got inside. Impossible to shake out. Quite a clatter if I shake it and probably rattles if going over bumpy roads.
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71 Superbug
71 Westy