I’ve actually experienced this on a brand-new Colorado (during an evaluation drive, no less). In this case it turned out to be a couple of loose fasteners in the front end, which were fixed quickly and permanently. In your case, though, it seems as though even with everything checked and tightened, the noise is still there.
So maybe it’s not something as obvious as a loose coupling or fitting. Maybe you’re looking at noisy shock absorbers. Sometimes these components can contribute a clunk, but it’s usually when they’re worn out, not on a six-month-old vehicle. Does the noise occur in a straight line or with some steering lock applied? Perhaps the steering lock stops are the culprits. I’d be putting the vehicle back on a hoist and checking that everything from the engine mounts to the cross-member and the steering rack to the transmission mounts are torqued to the correct values. Don’t rule out silly things like a loose tub or tray, either; sometimes a clunk in the rear of a vehicle can be transmitted down a chassis rail to sound like it’s coming from the front somewhere.
