Front Left Rattle

Thanks for the input. I did get a chance to get the truck on a lift and get under it. There is still nothing obvious, but one thing I didn't do while I had it on the lift was take a pry bar to various parts of the suspension to see if anything moved that wasn't supposed to.

I had the sway bar links replaced about 14 months ago and they still look good, but, that seems as likely a candidate as any right now, in addition to diff's recommendations of checking anti-sway bar mounts. I don't think it is related to any brake mounts as everything seemed solid there. I have it scheduled to go into the shop that replaced the sway bar links since those are still under warranty. This will be the 3rd shop that will have tried to diagnose this issue so we'll see what happens.

I don't see much discussion on here about the upper control arm bushings. Those looked fine but I'm wondering if it's possible that they're the culprit?

It turns out the front left rattle issue is in the air strut. Regrettably, I put Arnott remanufactured struts on the truck a little over two years ago and they've been nothing short of terrible, the front left has failed twice on me. Fortunately (or unfortunately) they are honoring the warranty. Since they no longer build the remanufactured struts, they are sending me their "new" part. I'm curious to know what could possibly be rattling inside, hopefully after it's removed I can get a better idea.