ronm; Are you saying, that a big hose dumping into the sump; Is the problem? {Because Dad's old 1964 4020, doesn't have any problems for 30 years, running a Shaver post driver plumbed this way, and neither does HT67, per his post}

Now, if something is wrong, inside the post driver's control valve, and constantly "dumping oil"; then yes, that would overwhelm the hydraulic system for the amount of flow.

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Rereading the original post, we are assuming that this comment is accurate:

 "This fall hooked it up to a shaver hyd postdriver and noticed when we raise hyd ram on driver hyd hose vibrates and hyd pump seems to cavitate "

Maybe we are putting too much, into this comment.

Does the post driver still operate?

Does the post driver's ram go up smoothly?

 Does the post driver's hyd. ram stay in the "UP" position when control valve lever is released? How about, if tractor is shut off? Does it bleed down? Does the post driver feel bouncy, like air is in the hyd. oil?

Have you tried a different hyd. remote (at rear of tractor)?

Have you tried and changed the hyd. tip, on that hose, for post driver?