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There is a tuned mass damper bolted between the frame rail and bed. The bushings get blown out and it wobbles around and makes noise. Not saying this is your problem but take a look. I cut the bolts with a sawzawl and was able to get it out(with a hammer) without having to unbolt and lift the bed.[ATTACH=full]456485[/ATTACH]
There is a tuned mass damper bolted between the frame rail and bed. The bushings get blown out and it wobbles around and makes noise. Not saying this is your problem but take a look.
I cut the bolts with a sawzawl and was able to get it out(with a hammer) without having to unbolt and lift the bed.
[ATTACH=full]456485[/ATTACH]