I have a John Deere 4640 Powershift transmission from 1978 with hydraulic front-wheel drive.
the 3 point jerks and it shakes very much when picked up (at any rotation) and if I leave it overnight with the 3 point raised it has dropped when I go out in the morning.
The suction screen looks fine, but maybe the suction hose is clogged? New filters. But not new oil.
What may be the problem?
A leaking hitch on a 40 year old tractor is normal, check the parking pressure on the remote hitch, you need 2250, if it is 1750 or less, the priority valve will not open fully making the hitch slow and rattles. The priority valve is positioned to reduce flow to the rear of the tractor, leaving priority to steering and the brakes. Check it out further.