Noise near or under drivers side of cab

[Dusilligaf]

2021 GMC crew cab 2500…Mystery noise.

I couldn’t track it down, my mechanic can’t track it down, and he’s pretty thorough…

It’s somewhere near or under the driver side…kind of sounds like going over a manhole cover, whithout going over one, or a quick rattle noise…mostly over light bumps

Only does it when cold or not driven a while….then it goes away, comes back EVERY morning when I drive it to work, or if it sits a while does it for a short time and then goes away.

It’s It driving me nuts. Any one had a similar issue, thoughts please….

[Another JR]

No idea here, but check you wheel lugs to make sure they are tight if you haven’t already. 

[Crazy Canuck]

I had a weird wobbly type noise that only occurred once in a while from the day I picked the truck up.  Turned out to be a missing fastener on the driver's front mud flap, the one that goes up vertically in the bottom.  Might be worth a check.