Can anyone teach me a little about how my machine drives and help troubleshoot my issue?!  Sometimes I hear a whining sound (like a relief valve is lifting towards rear of machine) and when I go to drive I have very little power and engine does not rev up.  However, when this happens if I lift the front bucket or curl the front bucket it operates well - engines revs right up and drives with full power.  First, how are these two things related?!  More importantly, what should I do to troubleshoot?  The dealer just repaired parking brake and had rear end pulled apart, no issues, new oil and filter.  It wasn't happening before that but I doubt that had anything to do with this problem.  I use Case HY-Tran Premium in rear end and Case TCH for hydraulic oil.  The hydraulics always work very strong...no issues there.  An when it does drive, it drives strong - Not that I do, but I can even start off driving in 4th gear if I wanted to.  I tested that out.