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Sounds like you have at least two different problems going. First off, I have to assume you have checked the oil level. Low oil could cause your lifting problems. The fact that the lift would not drop, yet you were able to push it down suggests that the ram cylinders are sticking rather than a pump problem. Cleaning the rams should correct that problem. A common problem with these older pumps is in the unloading valve. The system is designed to have 3300-3700 psi. The unloading valve spring can weaken with age and/or other parts can wear or break causing the valve to unload at much lower pressure. There is no way to get at the unloading valve with the pump on the tractor. Drain the oil and disconnect the linkages to the pump. The easiest way I've found for removing the pump is to remove the remote ram steel line from the hold position valve and then remove the two bolts holding that valve to the top of the pump body. There should be enough play in the rubber lines to move the valve out of your way. The pump itself is attached to the tractor by three nuts and two bolts. Removing the pump from the tractor is a little tricky as it is a tight fit but by twisting it this way and that you can get the oil pickup tube and cam followers clear of the transmission and frame. (Getting it back on can be even trickier and you may have to compress the cam followers a bit.) Now with the pump on your clean workbench (I always lay down a couple of layers of newspaper to soakup any oil) look at the front of the pump. There is a small access plate with a manual control knob. The plate is held on by four 7/16 bolts. Remove the plate carefully as there are springs under it. The plate covers two cylinders. The first outer cylinder contains the control valves (this is the cylinder under the manual knob). The inner cylinder contains the unloading valve assembly. The unloading valve assembly should pull right out but if it is stuck you can tap it down lightly with a hammer and it should pop right up. Be careful as there is a small check valve ball that may fall out the bottom of the assembly. Under that will be the upper spring retainer, an upside down bell shaped deal with a small rod (called a plunger) down inside the bell. (The plunger has a small hole drilled off-center on the upper end, the end that comes in contact with the check ball. Its gotta go back in that way.) Pull this out carefully as well since there are probably some shims on the backside that may fall off. Next is the actual spring (plus any shims that may have fallen off before you got the upper retainer out) and possibly some more shims under the spring. Inspect all the pieces for cracks or breakage. (I've got a tractor junkyard close at hand so spare parts are relatively easy for me to get. The price they gave me on all the pieces I've discribed above is $25 US.) If everything looks OK, you probably just need to add more shims. I've found that a couple of M12 washers under the spring work very nicely. You do have to be aware not to block the off-center hole in the lower spring retainer. Reassemble everything. A nice little trick for getting the access cover back on is to have two (or four) longer bolts (2 1/2 to 3 inch threaded all the way up the shank) with nuts turned all the way up to the head. Place the access cover over the cylinders and insert the long bolts. Now you can push down on one side and then the other, tightening the nuts as you go and work the cover down to where the original bolts will start. Its trail and error getting the right number of shims to bring the pressure up to specs (3300-3700 psi) so be prepared to repeat this process as needed. (In your case you may want to start with three washers.) I'd also suggest putting on a 5000 psi gauge in the small port on the top front of the pump (where the traction booster gauge would go) so you can monitor your progress. Of course you could have other problems, leaking check valves, etc. All of the check valves can be reseated with "a solid hit with a one pound hammer using a soft punch". The only exception to that is the unloading valve check ball. It can be reseated by pressing the ball into the seat with 5000 psi and then reaming the seat opening back to 3/32. Good luck!
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