Small Engines (Lawn Mowers, etc.): hydrostatic problems, snapper mower, rubber plug

Question
I have a LT16OH42CBV Snapper Mower that has quit moving almost.  When it gets hot then it will not move at all.  Seems that the belt is ok.  What can this be.  I noticed a set screw in the center of on of the bolts where the fluid will drain and it looks dirty but can not find where to add fluid.  Can you please help.  Single mother of 3.   Thanks Millie

Answer
you can try draining the fluid and replacing it but it may or may not help? If you drain it there should be a rubber plug on the top of transmission,if there is you should take it out and very slowly with a small funnel fill it back up with a good hydrolic fluid! Once you are done you will need to purge the transmission to get the air out. With it running on low rpm you should let the clutch out and slowly push the gear shift all the way to the fastest speed and then slowly back and into the fastest reverse speed.Push the clutch in and put it in neutral and then its time to test! Bring the engine speed up to normal operating speed,let the clutch out,and try engaging it into forward and just drive it a little bit forward and in reverse and see if it helped!
Hope you get it going,
Jason