D6c winch stopped working

i have a 64 cat D6C with a hyster winch on the back. When I first got the machine i was using the winch to pull out some stumps. The 1st stump i was able to use the short lever to pull it slowly. The next couple I couldn't get the winch to do anything with the short lever but the tall lever would pull them out in high speed. I shut the dozer off after the 4th stump to assess where to go next. After I started it up and pushed the lever nothing would work. After that I hooked the cable to the next stump and tried driving forward. The winch drum started to unwind like the brake wasn't strong enough to hold it. This past weekend I had some time to try and look into why the winch was not working. I first checked the oil level and it was good. I started the machine and started moving the levers to the winch with the machine at an elevated idle, when i pushed them either direction you can hear the motor tone change and bog slightly. Then I pulled off the top cover on the left hand side of the winch exposing the control valve. I cracked the 2 lines on top and oil would slowly drip out while the dozer was running. I pulled off the top rear hose and started the machine, it flows oil at a good rate but nothing high pressure. I located the screen filter (small square cover in the 2nd picture) there was some debris but nothing blocking it. With the filter off i started the machine and at an elevated idle i put my hand over the port the screen screws onto bit did not feel suction. When I removed my hand I could hear the pump making noise. I'm a bit stumped and I'm not sure what else to check or do to get the winch working again. Any help is greatly appreciated.