Abstract: A hydraulic wrench is provided of minimum external dimensions and yet constructed in a manner to be capable of exerting relatively high torsional forces. The wrench is constructed to be driven by a hydraulically reciprocal piston carrying a rack gear thereon with the rack gear meshed with a reciprocal sector gear having a pawl pivotally supported therefrom for driving a ratchet-type power wheel of the wrench. The wrench is provided with a variably positionable and reversable reaction bar or abutment assembly on the end thereof remote from the power wheel and the wrench further includes a secondary deactivatable ratchet pawl for preventing reverse rotation of the main ratchet-type drive wheel of the wrench.