JLG 660SJ Service And Maintenance Manual page 172

SECTION 4 - BOOM & PLATFORM
7. Remove stop tube if installed.
8. Actuator has timing marks for proper engagement.
4-22
9. Before removing shaft, (2), use a felt marker to clearly
indicate timing marks between shaft and piston. This
simplifies timing during assembly.
10. Remove shaft (2). It may be necessary to strike threaded
end of shaft with a rubber mallet.
– JLG Lift – 3121298