Ford 2003 Mustang Workshop Manual page 2518

8. NOTE: Coat the piston seals and clutch drum sealing area with petroleum jelly.
Position the special tools on the clutch piston.
9. Using the special tools, install the forward clutch piston into the clutch drum.
Push the piston to the bottom of the drum using even pressure.
10. Using the special tool, compress the piston return spring and install the retaining ring.
11. Slowly release the press pressure and remove the forward clutch.