This Preliminary Information communication provides the technician with the steps on repairing a clunk noise after shifting from reverse to drive or drive to reverse and then accelerating. The concern is only with rear wheel drive 6L45 or 6L50 automatic transmissions with Regular Production Option Code MYA or MYB apply. Apply thread locker to the transmission output shaft flange splines and install a new front propeller shaft flange nut. Apply thread locker to the new propeller shaft flange nut if it does not contain a pre-applied adhesive patch.
