I sometimes get this strange rattle when my BB is coasting and downshifts while in lower gears, usually around 20-25mph. No shuddering or anything that feels out of place. It doesn't sound like the old familiar valve rattle, but I notice this typically when going up/down small'short rolling hills and giving very little application to the accelerator or when firmly (not hard) braking and the vehicle downshifts. I've never owned anything with less that six cylinders, so maybe it's no big deal. It's hard to replicate on-demand unless the planets align, or I would have taken a a trip to the dealer already. Anyone else notice this or have any suggestions?