The juddering can be caused by a few things:
Stuck Suction valve on the pump ,(There are four ) effectivly reducing the hydraulic pump flow by 25% OR A stuck discharge Valve but less likely as this would reduce the hydraulic oil flow AND discharge pressure.
Incorrect adjustment OR damage to the hydraulic control linkage which can in some situations cause the pump to Judder.
Broken Pump locating dowel pegs allowing the pump to Float ( move back and forth inside the Transmission housing )which in some instances can be related to the last point.
Broken dowel pegs are reasonably common usually caused by P.T.O.driven implements being fitted and the P.T.O. shaft being to long resulting in the shaft effectivley being TO long in the fully compressed state ,this will only be obvious when the linkage is RAISED TO THE TRANSPORT POSITION ,this then PUSHES the P.T.O.shaft into the gearbox and the first obstruction is the Dowel Pegs, to check ,do one at a time, drain the the transmisssion oil,Look for the small oval shaped plates with two Studs/Nuts, 1/2 a/f spanner/wrench.
remove either one by undoing the two nuts on the peg flange ( near the bottom of the transmission housing about where your Heel would be if your foot was on the Clutch/Brake ,remove the peg and if all is good the peg will have the small dowel on the end ,if broken the peg will come out as a flat plate ,if you find the peg IS broken it is possible to replace by using a magnet to remove the broken piece and fitting a new peg.
I should mention ,ONE reason the shaft is telescopic and one that is quite often overlooked is the fact that the P.T.O.pivot point is not on the same Axis as the Linkage which results in the shaft Extending When the linkage is lowered AND Compresses when the linkage is Raised .
Just another important point on P.T.O. shafts :
The safety shield should always be operational and in good serviceable condition,always check BEFORE use.
Lubricate the two halves of the shaft and always check that the shaft is indeed telescopic and is travelling within the areas of operation that is , when fully compressed the shaft should still be able to be compressed at least another two inches with the Linkage raised to transport ,a good guide is that you should be able to ,with the P.T.O.shaft connected to the tractor and raised to the Transport position try to remove the shaft ,it should slide off at least two inches if it does ,lower the linkage ,down as far as possible and remove the P.T.O. drive shaft and check ,make sure there is at least say three/ four inches of shaft engagement if all is o.k. you are good to go.
A restriction on the hydraulic supply to the pump can also cause the pump to Cavitate ,(Draw in air) ,which will cause the pump to Shudder ,most common cause is a blocked Suction filter.
The Three point Linkake toplink draft spring adjustment can also cause the hydraulics to Shudder if the spring is either broken or out of adjustment.
There are other faults that can affect the pump performance but the points above are the most likely to cause Juddering /Pulsation of the system, if you consider the fact that the pump is a four cylinder unit and if one CYLINDER was not operating properly it would cause a miss , kind of like a four cylinder engine with a bad Spark plug.
Adding External hydraulic supply:
I see no reason why providing there is a hydraulic pressure releif valve in the system that does not allow the pressure to go above the factory pump pressure which can be as low as 2250 to 2550 to be on the safe side.
To introduce external supply make sure the hydraulic control levers are both in the down /lower position and stay there undo the two setscrews that locate the transfer cap ,the one with the standpipe attached and rotate the cap 1/2 turn effectively blocking the PUMP supply to the linkage then removing one of three plugs on the lift cover,one either side near the front of the cover ,3/8 inch bsp/npt dry thread or the one on top left hand side . the NUT has TWO flats and is sealed by a Dowty Washer ,a steel washer with an O ring type seal inside ,you can connect to this using a 3/8 Inch BSPP fitting.
If You fit a Three spool hydraulic control valve you will then be able to operate the linkage using a SINGLE ACTING SPOOL VALVE ,Pull to raise Release to Hold and Push to lower the linkage,and the other two spools to operate the front end loader, bear in mind that neither the original pump or controls will be operational and to avoid the possibility of the pump running under constant pressure ,make sure tyhe quadrant levers are secured in the down position.
You can still buy a front mounted pump drive shaft and hub which bolts onto the standard front crankshaft pulley ,the bolt holes are already drilled and tapped on the engine pulley ,just check some tractors did not have the holes ,there are lots of pumps that will suit , a pump with say 10 to 12 gallons per minute would be enough any more and you will find that you will stall the engine when using the loader.
Thats all for now, Beer O' Clock.
Happy Days.
Hutch.
