Look underneath the vise you will see a semi circular plate covering the screw and nut connection. Undo the single bolt to remove this cover plate. Now remove the small flat metal plate with three holes from the end of the vise threads! Engage the release, 2 turns counter clockwise of the vise handle if I recall, and remove the front vise jaw from the body mounted on your bench. NOTE: mark on the nut that engages the middle thread which way it sits on your central thread because the direction is important! DAMHIKT
Clean the threaded rod of all junk, and use some white lithium grease (you can get a small container at Canadian Tire or any auto parts store) to lubricate the center thread and nut. Revearse the removal directions & install everything making sure to get the nut in the correct orientation!
– Quest in Calgary on the Canadian Woodworking Forums
Quest explains how to keep the York Quick-Release Steel Bench Vises from Lee Valley in good working order. Mine is starting to feel like it needs this kind of TLC very soon.