Hi Tim
Mate it is a very simple OH, there are about 5 small components to replace. They should cost around $25 dollars from Yingling. Just as FYI, they list a new unit at $23,000.
During my rebuild I collected another two units as spares. Follow the maintanence manual as it is a simple OH, when it comes to recharging with nitrogen, mine took 380psi. It should take about 2.5lbs to pull the door down, what I also did was recharged mine so that it would lift the door 80% of the way up, then with a gentle touch it goes the rest of the way to the rubber stop, that way it doesn’t bang against the stop.
I have since rebuilt one of the spares as well, but not re-gassed, takes me approx an hour to rebuild a unit. Don’t touch the gas chamber.
When you pull the shaft out and drain the oil, watch for the little ball bearing that will fall out.
Dave
