Man, I'd love to ride in your Yukon to hear this for myself. I'm about to spend $60K on a Yukon XL SLT or a Suburban Z71, seriouslly hope I don't experience this. I'm in a rental 2015 Burb LT right now and I think it's just fine.
I asked the tech, Mr. Merck, to post on here in a private message. Don't blame him if he doesn't want to publicly post on this debacle.
He responded with:
"I was convinced of the same thing. We did the headliner/roof bulletin first. It had no effect. However, I have heard that it fixed some trucks."
You can PM him if you have questions, he will probably respond.
A tech said they replaced entire rear end to fix pressure issue. See Mr Merck posts in this thread :
http://www.tahoeyukonforum.com/forum/showthread.php?t=67851&page=4
Good stuff. Looks like you guys are narrowing this issue to the ANC. Hopefully GM Engineers are watching this thread and will have a solution for everyone. Sounds like this has cost them millions already in buy backs and warranty repairs! (well, probably not...they are reselling the buy backs)