Case 580 B shuttle transmission

I just purchased a case 580B constuction king backhoe. The shuttle transmission whines in reverse. Pressure guage is in the green zone. Fluid is a little low and looks milky. Is the whine in reverse a serious problem? Will fluid and filter change help? How does the fluid get to be milky? My first guess would be water in fluid,if so how does the water get in transmission?
Hydralic fluid appears to be in the same milky conditon. Is the shuttle transmission and hydralic fluid one and the...

Case 580 B shuttle transmission

Case 580 B shuttle transmission