I have a Shibaura SD3000AO tractor. The hydraulics will only produce about 1000#, without blowing through a bypass??

This company can get you a service manual which can lead you to the relief valve,, this tractor will have a relief valve built in the hitch valve area under the seat, follow the small line fromt the pump up to the hitch and it will be in that area, ,a few questions,

what are you doing with the tractor when it acts up.

does it start out strong and get weaker as it heats , up ,

do you have a loader on it.

will the loader work with full pressure ,

where are you checking the pressure at and is it cold or hot

Let me know and I will try to hlep you through it thanks Kevin K

first most tractors are plumb from the pump through the loader valve then back in to the hitch top on the tractor , so when the loader lever is pulled all the way the hitch would stop for that time , this is the way all open center systems work which ever is first in the system , if you where working both and the loader did not need all the flow then the mower would raise at some rate also, these over seas unit are mostly alike , your loader valve also has a relief in it as well as one in the tractor,, so if it leak by when working the loader or the hitch it would bypass oil and slow the rate of travel and power, if the unit is getting weaker as it warms up I would suspect the the pump , the relief valve is not common to fail in either hitch or loader , probably 30 pumps to 1 relief valve problem over the years

you can really only check the pump with a flow meter to be sure, but if you put a gauge in the line going to one of the cylinders and raise or lower it to the end of the stoke, you should see the pressure do up to what ever it can build, then work the loader up and down and warm up the oil and see if the pressure drops , relief valve do not change settings they are either leaking by or not and will do so at what ever they where doing when it was cold

check these things and i believe you will find the pump is only able to put up 800 to 1000 psi and the bypass you are having is in the pump its self,

I forgot to give you the link to the company tath can get you the book and parts, once you get the part number you can serach on line for the best price. http://southern-global.com/

I have bought pumps from this link http://www.compacttractorhydraulicpumps.com/index.html this is all they sell I believe is hydraulic pumps for compact tractors LEt me know if I can Help you find any more info ,Thanks Again Kevin K