While I'm on the subject of this Grove RT63S rough terrain crane have one other question. I have just about no history of this crane and only see it maybe twice a year when it comes to our quarry to lift something here for repair. Seems we spend more time fixing it than using it, but that's another story. One thing that does not seem right to me is related to the transmission pump mounted on the back of the converter housing. On the pressure side of this pump there is a brass petcock teed into the elbow. Anytime this crane sits unused for a day or so you have to start the engine and then crack this petcock open to bleed off some air before the machine will move. I was wondering if there is suppose to be a check valve in the suction line down by the sump that has failed and this was a quick and dirty fix someone came up with late one night many years ago. Besides being a pain when one is working alone I don't think starting the pump almost dry is good for it and the bleeding of the oil just adds to the mess of this machine.
Sounds like the pump might have a little wear or a suction leak in a line or hose