Your tractor has common fluid for all functions. I recommend when ever anyone purchases a "Grey" tractor or any used tractor that you change all fluids and filters immediately before use. You do not know when they were changed last. It is also a good idea to get some oil sample bottles from a local dealer and submit the original oils for testing. Ongoing sampling is also a good idea as it will tell you if there is possible premature component wear or contaminants in your fluids. Who knows... to get the "grey" sold they may have topped up the TDH fluid with engine oil or even water! As for the shuttering of the loader, it could be lack of fluid, wrong fluid, weak pump, too low RPM, was the hydraulic system hot?