HELP!!! 340 utility hydraulic weird stuff

Hey all, I recently found this site and its great. I have a question and need help. I just bought a 1962 340 utility, nice tractor. Only thing is, there is a whine like the hydraulics, under steering wheel and/or inside tranny. Here is the weird part, it robs engine of power. When I raise/ lower three point hitch, it quits whining and engine runs perfect. I mowed some the day I got it, 91 inch finish mower, pulled it in 4th gear half throttle. Now bogged down in 3rd. Weird that it quits when I use the hydraulics, comes back when I'm not using them. Fluid is full in tranny. There is a filler cap at end of distributor, where governor is, this has to be engine oil fill, right, and not hydraulic? Could this be a valve stuck? I have a 44 H, 50 H, 52 H, and have been around those my whole life.
Any help is appreciated. Oh, the shifter tag has the D and T/A on far left, but it doesn't have the lever for it, so I just assume it doesn't have torque amplifier. Man said it didn't. It came from Southeast Missouri, not mentioning name of dealer.

You hydraulic system is staying on demand. In other words under pressure. First thing is look at the ends of your hydraulic valves. There is a flat on a stem to turn valve from double action to single action. Often times the roll pin gets broken or bent allowing stem to be turned too far. If all valves check ok, then you have a problem in the regulator valve block. It is the valve with four bolts on cover. Under cover is heavy spring so caution if you take it off. I use longer bolts in two corners. You will find a screwdriver slotted orfice with screen. It is probably plugged. You will need new gasket though if you take cover off nine times out of ten.

Hi, many years ago when we had a 300U and hydraulics
started to whine, it was time to clean the hydraulic
input filter screen in the hydraulic reservoir under
the seat. Not familiar with 340U but would guess it
has a similar setup to 300U.

JimB

(quoted from post at 18:38:43 06/29/13) You hydraulic system is staying on demand. In other words under pressure. First thing is look at the ends of your hydraulic valves. There is a flat on a stem to turn valve from double action to single action. Often times the roll pin gets broken or bent allowing stem to be turned too far. If all valves check ok, then you have a problem in the regulator valve block. It is the valve with four bolts on cover. Under cover is heavy spring so caution if you take it off. I use longer bolts in two corners. You will find a screwdriver slotted orfice with screen. It is probably plugged. You will need new gasket though if you take cover off nine times out of ten.

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Thanks so much. Are the valves that switch from single to double action on the outside of those valve blocks? I don't have the manuals yet, but are ordered. Thanks so much!

340 has an odd draft control system if it is quick hitch --mine had a mind of its own[ hydro touch] I had to manualy control the hyd.they would lock in up or dn and stall the engine.--the control rod comes out of the seat base to the middle of the consol after 20 yrs I put a small control valve in the pressure line and routed it back to the gear box ---to this day I don't know why I waited so long---that will solve your problem

(quoted from post at 00:05:26 07/02/13) 340 has an odd draft control system if it is quick hitch --mine had a mind of its own[ hydro touch] I had to manualy control the hyd.they would lock in up or dn and stall the engine.--the control rod comes out of the seat base to the middle of the consol after 20 yrs I put a small control valve in the pressure line and routed it back to the gear box ---to this day I don't know why I waited so long---that will solve your problem

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Hey guys,
I really appreciate the responses and help! Pete23, the spool(I only have one) still had pin in it and was just as it should be, so I took that cover off the regulator block, pulled orfice, and it was clean and I could blow thru it, so put it back together(IH dealer had to order gasket of course), used old one with a little blue gasket maker, and all is good there, no leaks. But still had whine and power loss. On this tractor, the adjustment handle for the Tele-Depth has been broken off at some point, and I got to thinking about what you and Roger said, about valves being centered, and low and behold the tele-depth was NOT centered, and was "correcting" except for when I was raising or lowering the hitch. Got that centered and it runs like a top now, smooth, no labor. Thanks you guys for the insight and help!