an improved hydraulic wrench including a one - piece housing in which one end of the housing forms internally a cylinder for hydraulically reciprocating power and the second end of the housing includes an opening in which a torque arm / ratchet mechanism can be pivotally connected by , for example , a square shaft . there is further included a piston shaft which has a fixed piston on the first end and the second end includes an elongated slot which provides a flat wall at 90 degrees of the reciprocating power source . the wall in the elongated slot allows the drive pin which connects the ratchet mechanism to the piston shaft to roll up and down during cycling of the tool , and provides a non - pivoting reciprocating power source as the piston shaft moves backward and forward during operation . there is included a ratchet wheel fixed to a square shaft for rotation therewith , a ratchet pawl on the drive lever and engaging the ratchet wheel to rotate the square shaft upon reciprocation of the piston shaft in the cylinder .