HYDRAULIC DRIVE OF WORK MACHINE EQUIPPED WITH CRAWLER-TYPE TRAVELING DEVICE

A hydraulic drive system for a working machine including a track device of crawler type is provided. The track device of crawler type travels with hydraulic fluid supplied from at least one hydraulic pump to right and left track motors. The hydraulic drive system is capable of easily correcting skew traveling for straight line traveling without having to replace a track motor or other large-size device and without having to specially modify a main circuit. A traveling test is conducted upon shipment from a factory. If skew is noted during the test, a plug 65b disposed on the side of a valve opening-side pressure receiving portion 28b (or 28d) of a pressure compensating valve 27b (or 27d) for track whichever is lower in speed is removed and, instead, an adjusting mechanism-mounted plug 37 is mounted. An adjusting pin 37b of the adjusting mechanism-mounted plug 37 is operated so as to strengthen a biasing force of a target compensating differential pressure adjusting spring 36b. An opening in the pressure compensating valve 27b (or 27d) is thereby corrected in an opening direction and a flow rate to a left track motor 6 (or 8) is thereby adjusted to be equal to that of a right track motor 8 (or 6).