Just got back from dealer. Had them look for a clunk/rattle I get on some mildly bumpy roads for the 3rd time. I've also looked with no results. Now they think it may be the top helper spring hitting the rubber stops but I don't think so. They want me to see if I hear it when loaded. (the truck, not me:beerchug:) I've eliminated the tailgate, draw bar, spare tire and pretty sure it's not the exhaust. It's definitely in the differential area. I've ridden in the bed and can hear it clearly.
Any other NBS DRW owners hear this?

This does sound exactly like the helper springs hitting th bump stops. Our '04 LB7 does it and my new '08 LMM dually the same thing. Both trucks have done it since day one! The sulastic shackles are suppose to help this I believe.

Thanks. I have a call into Nick about the Sulastics.

Mines does that too. I was worried there for a while. Someone on here told me about that.

If I hit a bump just right it sounds like I'm riding in a clunking/rattling POS! I love my truck and a hard core GM man but the noise has to go.

My 03 Dually does it too.

Just put an extra 1,000 lbs in the bed and the noise will stop :)

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Its no big deal, don't focus on it and it will go away. lol