I have 140k miles on my cayenne and have kept up with it really well. I've already replaced the cardan shaft busing with an EPS one and replaced the front control arms about 30k miles ago.
I'm not sure if it could be related, but a week ago I changed my front pads (eps yellow) and rotors (x-drilled) and within a few days, I started hearing this really strange sound. It almost sounds like I have a baseball card sticking in my wheel spokes, but more metallic and off and on. Sometimes it'll make zero noise, other times, it's a loud, tinny pop, like tapping a tin can w/ a knife. (usually decel) and others it's more of a deep thump, as if you tapped the diff case w/ a hammer (accel). It follows road speed and not engine speed and sometimes it will stop when I get past a certain speed, others it just gets really fast. Also, I noticed today, when I was at about 60mph and accelerated around a slow car, I felt a vibration through the throttle and maybe even steering wheel a little.
I thought it could be with my brakes, so i took them back apart, inspected everything and put it back together, wiggled the suspension all around and turned the wheels (no wiggles anywhere). The only sound I could hear was on the drive shaft that goes from the transfer case to the front diff, when moved back and forth, there would be a metal-on-metal click on the transfer case side, but it sounded different enough from what I was hearing when driving and that it should be under constant load and not the cyclical load i'm hearing. I think that isn't the issue. The noise had stopped for 2 days afterwards. Then, today it starts again. I hear no change with turning of the wheels or height of the car, or any change if and when I depress the brakes.
I'm baffled. I tried getting a video if it, but just my luck when I had my friend to record the sound, it wasn't doing it.