OK< thanks for more info, , the more info you give us, the better we can try to help you
first off the chain case, is oil for your drive chains(there is one case one each side)
this has nothing to do with your hydraulic system(unless they share the same fluid(not sure on your exact model< but most have separate fluids for chain case, and then a separate system for hydraulics)
you should have a hydraulic tank in your engine bay area that shows how much fluid is in it, , if LOW< it can/will cause issues!
thus why I asked if its full or not
next , if your hydraulic fluid is OLD< lots of hours on it, can sort of wear out and not be as good as it should be, , again could cause issues!
NOW< if your saying things run GOOD< for an hr or so, and then things start to go bad, make this noise
it could be, a motor issue, like low compression, as a motor gets hotter, it can lower compression, and if its already low, , it can then not be able to make enough compression to make proper power! , to power things(run hydraulics's
thus stalling or wanting to stall motor, and making hydraulics's not function properly, which can cause sounds like growling or squealing! as the pumps cannot make enough pressure to power things, when there isn;t enough RPMS going to make hydraulic pressures needed!
SO< I think what you again need to do first here is confirm that the hydraulic tank is FULL , at correct level, and pending on how many hours are on machine, and fluids, , it might be a good idea to replace fluids and filters, to also confirm none are dirty and or blocked!
there should be fuel ,motor oil and hydraulic filters,
I am also going to suggest to you to get yourself a service manual , this will tell you all about your machine , where everything is, and how to fix everything on it, there worth having
there are these days both hard copy physical paper copies of them, and they can be found online in PDF files., pending your age and like or dislike of modern things, , you get to pick what one to get,
used ones can sometimes be found on ebay, and like places that sell new and used items
if your not that well at repairing things, or have much experience with machines like this, you might also, want to ask around to your friends and family, and see if anyone there is, and can help you find your issue
as we online are not there to see, or hear things in person, so were all kinda guessing, which can help for sure, but nothing beats having someone there with machine that has some know how! to help you!
