I have this annoying little problem when attacking the back roads. Emphasize on that because it apparently doesn't happen unless I drive it hard after a while, assuming the trigger for the rattle is a hot environment.

When I drive the car hard after a while, and make high speed left turns, I can hear this rattling noise somewhere under the center console/transmission tunnel. It sounds like little rocks hitting a heat shield. However, I took a look under the car and I couldn't spot anything that's loose or may be hitting the heat shield. So maybe it's something directly under the shifter area? That's the closest I can pinpoint it. Anyone else know what I'm talking about?

 

Maybe it really is "little rocks hitting the heat shield"?
This is a reasonably common thing with XFs - small rocks, pebbles, bits of gravel etc get up under the central tunnel heat shield and make a helluva racket.
In your case it could be that when cold the heat shield is "shrunk" and the rocks are jammed, but once you get things good and hot the heat shield expands enough for them to start rattling around.
Try getting underneath when things are warm rather than hot and tap the heat shield with something reasonably soft in a few places and you might just hear your rattling rocks.
If you do, remove the heat shield and see what falls out!

 

I'd laugh my head off if it really is that simple. Though it does have merit - I unmounted the bottom plastic tray that protects debris from hitting the transfer case, and good god it was just a tray full of gravel. I don't know why they didn't make it flat, or bent toward the front so it's like a front-facing shield, rather than a pickup tray. I'll see about just making a racket with the heat shield around that area, see if I can get some gravel out.

 

It is likely a heat shield. I had similar issue on my car, where it would rattle but only under wide open throttle condition. The fix was re-adjust heat shield above transmission.

 

I still can't figure it out, so I recorded it, hoping someone can help me diagnose. It's actually happening more often now, even from just short periods of normal driving.


Ignore the constant rattling in the background, it's a trim piece I think...haven't pinpointed that either. Listen for what sounds like a wiring harness tapping on metal, especially towards the end of the video. That's what bothers me to no end. I know for certain the sound isn't there on idle or driving on smooth surfaces, so it only sounds off when a force is exerted on the car while driving. It also shuts up when I turn right; I believe the force from turning right forces whatever that's rattling to move away from whatever it's rattling on.

 

Have you gotten under the car. One of the two massive heat shields in the tranny tunnel could be loose causing the issue.

 

I did...tried banging on the heat shields and playing with it, but I can't reproduce the noise. I might just have to take the whole shield loose and see if there's anything beyond it.