Check the filter bypass valve if it is bad it will dump charge oil back to sump. you should have a min. of 5 psi charge pressure at the pump. I am not sure about the spec but you should have about 5 gal a minute of oil all the time suppling the pump. that 175 psi you got is the powershift trans oil pressure. If you can't find the filter bypass valve let me know I will look it up.
Good Luck Ed