Ford 2003 Mustang Workshop Manual page 2746

14. NOTE: If not done so previously, soak the blocking ring in MERCON® Multi-Purpose ATF
Transmission Fluid XT-2-QDX or equivalent for ten minutes.
Install the fourth speed synchronizer blocking ring.
Align the notches in the synchronizer blocking ring and the synchronizer hub inserts.
15. NOTE: Verify that the fourth speed synchronizer blocking ring is still in position.
Align the flat on the fourth gear clutching teeth with the countershaft cluster gear and install the
input shaft.
16. NOTE: Do not install the end play shims at this time.
NOTE: Do not apply sealant to the input shaft bearing retainer at this time.
Install the bearing race in the bearing retainer.
17. Install the input shaft bearing retainer with the notch facing upward.