I recently bought a 973. S/N 66G00946. It had been sitting for several years and I’m trying to get all the bugs worked out of it. Changed all fluids and filters and all mostly works good. I’m having an issue with the boom drifting down. Slowly most of the time but once I get to working it it will continue to drift fast from time to time. I just have to bump up on the lift lever and it stops until the next time. I’ve already replaced all the cylinder seal kits but I assume this is an issue with my spool valve. Anyway to test this valve or something?
Is the linkage sticking a bit? Try lubricating it before you go yanking the spool apart.
The linkage for the lift and tilt are really good. Both move freely. The old hydraulic oil did have water in it.