Sounds like what the other posts have already stated,..you lost prime on your hydraulic pump. There should be a plug on the top of the pump towards the front. You can unscrew that plug, or the hydraulic line and check for oil. Pour some in if you need to prime the pump. Also be sure to bleed the air out of the system after you have primed it. Check your hydraulic oil level at the dipstick to ensure the sump is indeed full. I included a picture of the vane style pump. T.O.H. (This Old Hokie) on this site can give you all the info you need to get your pump primed and he also has a replacement gear style pump kit with fittings for your NAA if your pump is bad.