Toshiba E 523 jamming at registration on 11 x 8 1/2 only

[arriva1]

This copier jams at the registration on 11 x 8 1/2 only, not on 8 1/2 x 11R or any other size. It will run a few pages then jam up. I have replaced every feed unit, the transport unit at the turn, the registration unit, the motor, the NVROM chip. I just cant seem to figure out why it jams. If anyone has had this problem or has any ideas, it would be greatly appreciated.

[vmchong]

Check the Reg Clutch, clean it with alcohol.