In this particular diagram, the thrust washer (4228) is shown incorrectly between the L/H axle side gear (4236) and the clutch hub (4946). The thrust washer should be fitted over the spigot of the clutch hub so that is located between the clutch hub and the differential case cover.
The sole purpose of the L/H thrust washer is to prevent the clutch hub from galling the inside of the cast iron cover should the clutch friction plates be excessively worn away.
Tom