2006 Dodge Ram Gear Noise

Just curious if any other Ram owners (or other models, too) with a manual transmission have ever experienced any gear noise.
We bought this truck new (it's the 2500 Power Wagon model) and it
started out making this noise in 2nd gear periodically (we first noticed it when we started to tow our TT) and now it happens all the time - still in 2nd gear.
The noise sounds like a rattling chain (like the safety chains are temporarily dragging on the ground) when letting the clutch out in 2nd gear. Of course, when we brought it in for warranty work, the mechanic 'couldn't hear it' when he did a test drive. DH is going to bring it in again and drive with the mechanic another day when we have more time.
Anyone know what this noise could be? We're stumped...
Thanks, Paula
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