727 / 46RE / 47RE / 48RE, Billet Steel Rear Clutch Drum (Forward Clutch). This Rear Clutch Retainer is manufactured from 4140 HTSR billet steel vs the O.E. cast part. The O.E. cast Retainer is known to fail, (see photo below) therefore, this TCS high strength Rear Clutch Retainer should be considered when using for commercial, heavy duty and in certain raised line pressure applications.