Carrier bearing failure would be a lot more noticeable than just a clunk. Like Bob said, some noise and clunks are normal in 4x4. Even some deep howing noise is normal due to having an additional axle engaged. You aren’t going to hurt your machine running on pavement or the trail, but you’re going to have some noise in 4WD since it’s physically impossible for the front and rear to spin at different speeds. Many term it “ratcheting”, especially when turning on dry pavement. FYI, don’t run long periods of time on dry pavement in 4WD. It’s very easy to overheat the front diff and engagement clutch. Applies to all part time 4WD systems.