G,Day Mr joe.
The service tool is ,was made by Litchfield the English specialist tool company ,I have had mine for more than 000000 years.
It would not be hard to make in fact you may be able to use one of those hydraulic ram PEG spanners the one that looks like a set of engineers calipers with two dowel pegs on the end.
Or use a big screwdriver ,place it over the top of the shaft behind the linkage yoke and line it up with one of the notches ,You will get what i mean when you have a play ,dont forget tighten the nut up till it starts to show LOOSENESS AND BACK IT OF TILL THERE IS NO SLACK usually about one turn,and tighten the grub screw to lock it up .
Put an implement on the tph and with the engine SHUT OFF and the lift linkage LOWERED to the ground ,all pressure released from the system ,unscrew one of the blanking plugs on the lift cover front left or righ hand side OR the one on top with the plug that has the two flats on it 3/8 npt Parrallel thread ,or the side ones have 3/8" nptt,fit your hydraulic pressure gauge ,3000PSI and start and lift the hydraulics all the way up to CONSTANT PUMPING Slowly, you should hear the releif valve hiss and the engine slow down a tad pressure should be around 2250 to 2550 anywhere around there will give you satifactory operating performance, I would not pull the pump if it was above two thousand PSI.
You will most likely find that if the draft spring has been frozen when the initial hydraulic adjustment was done you will more than likely find the internal adjustment has to be done ,just to fine tune the hydraulics ,if you do need to it would be a good idea to remove and clean the hydraulic filters and the inside of the gearbox when you are at it.
Thats all .
Happy Days
Hutch.