Some 2011-2012 Lexus MY GX 460 vehicles may exhibit a rattle noise from the second row passenger side seat back cover area while driving over rough roads or bumps. This noise may be coming from a mass damper located under the seat back cover on the seat frame. A revised damper has been developed to address this issue.
This applies to vehicles produced before VIN JTJBM7FX#C5040731 or JTJJM7FX#C5040734.
Confirm the noise. This rattle noise occurs due to insufficient insulation on the mass damper in the seat back.
Remove the rear seat cover cap. Use a plastic pry tool to detach the claw. Remove the rear center back lock control lever (remove the two screws, move the lever in the direction of the arrow to detach the guide and remove the lever. Detach the cable clamp and disconnect the cable from the lever).
Remove the rear seat back cover. Press the seat back lock release button to release the lock and fold down the seat back. Remove the rear seat back board subassembly RH (remove the seven clips and remove the carpet).
Remove the two bolts that secure the dampener and replace with the upgraded dampener P/N 71499-60020 (note that this is also the old part number. The dampener has been upgraded but retains the same part number). Tighten the bolts to 4 ft-.lbf.
Reassemble the seat subassemblies.