I will check into testing the pressure.
It has probably been 2 years since the fluid & filter were changed and the screen cleaned. I did this when I first noticed the PTO coming to a stop under a load. It hasn't been a priority to have it looked at as I normally just use this tractor for light duty stuff such as pulling a drag type hay rake, loading hay, etc. Normally the heavy mowing (or other things that are PTO operated) is done with one of our other tractors. This tractor isn't getting much of a work out this year in the hay department due to lack of rain so I am trying to get it back going to do some clean up around in smaller areas. Therefore, I need it to be able to pull our smaller bushog.
Thanks to all that have resonded for the help and things to look for.