Long 445DT

There is a socket on the left hand side of the seat for a lever(missing) that seems to work the main clutch via a cable. This is not the PTO hand clutch, I know about that. Is this a special or a standard fitment? Any ideas why?

There is a good quick detach front loader with three remote operated spool valves in the cab (one spare). To get this to function you have to hold down a lever on the right of the seat, near the rear lift & draft control quadrant. The loader levers them work normally. This lever seems to work a master hydraulic valve under the seat & since it is painted the same blue as the transmission, I assume this is a factory fitment. What does it do when you lift it? Does it direct fluid to the rear Q/D outlet?
There is one Q/D outlet at the rear, I need to connect a backhoe which has two hydraulic leads, one in & one out - assuming the existing Q/D will supply the backhoe, where do I plumb in the return?
I've noticed forum threads recommending cleaning the hydraulic/transmission oil filter in the tube under the starter - can this be removed & cleaned without draining the whole unit?