Welcome aboard. There is a Hydraulics forum here on TBN and by reviewing it, you may find posts in regards to your inquiry. If you require further assistance, you should receive more replies by posting your questions in that forum. Best Wishes.
Get the operator, repair and parts manuals before you tear into the 135 hydraulics (mine is a 1964 MF135 diesel deluxe with multipower). What's wrong with the hydraulics on your tractor?