Ford 2003 Mustang Workshop Manual page 2748

21. NOTE: If not done so previously, soak the blocking ring in transmission fluid for ten minutes.
Install the fifth speed cluster gear, the synchronizer blocking ring, the synchronizer assembly,
and the fifth gear shifter fork as an assembly.
22. CAUTION: To prevent component damage when installing the extension housing
(7A039), the alignment tab on the reverse brake ring (7M000) must engage the alignment
slot in the extension housing.
NOTE: If not done so previously, soak the blocking ring in transmission fluid for ten minutes.
Install the synchronizer blocking ring, the reverse brake ring, the thrust washer, and the fifth
speed synchronizer retaining snap ring.
23. Apply pipe sealant to the reversing lamp switch threads and install the switch.
24. Install the reverse gearshift lever retaining clip.