rebuilt the final drives on a komatsu pc150-1 and now they are turning backwards, lacking power and are making a grinding noise. what could be the problem?
If they are turning backwards you probably swapped the motor hoses. Lacking power and grinding is not good at any time. Do the level and drain plugs have magnets on the ends. I'd start there for troubleshooting.
Grinding? Not sure, but, the power and direction I can help with. The swashplate is in backwards. The direction reverses and the hi/lo's swap when the swashplate is in backwards. The drawings in the service manual show a dot on the plate, and there is a dimple on the plate. They do NOT correspond to each other. Pulled a PC 300-5 final apart THREE times to get it right. The shop guys would tear it apart, to help me, before I could clearly mark thing before disassembly. Third time, I tore it down.