ok i know i found this issue on another jap brands i.e lexus ,toyota,nissan, i have noticed that the lower seatbelt mounting bolt has a shoulder machined into it and in my opinion it is too long as this allows the lower seat belt buckle to rattle along the length of the shoulder i made a plastic spacer and the covered the ends with some self adhesive felt and this cured it.
i have attached a very rough drg but for arguements sake say the lower buckle is 6mm wide and the shoulder is 10mm long it can then move 4 mm along the bolt
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