Evening Don, Walter,
They have the planetary gear types that only require fifteen gpm.
I bought the thirty gpm for two reasons. The first of course was if I wanted to move up to a big tractor I wouldn't have to replace the auger motor. This includes the situation where I felt I needed to rent say a ten thousand pound skid steer for a job. I would have the big unit already.
And secondly it's along the line of why I have a big block in my truck. I'm a firm believer in the big dog loafing pulling the load is gonna last longer than the little one killing itself to do the same amount of work.
My machine has fourteen point three gpm at a top rpm on the low side auxillary hydraulics. I use this ninety percent of the time for one reason. On the low side I have a forward reverse pedal on the floor. But on the high side where it's twenty eight point six gpm I have only single direction electronic switch off and on. I lose the control, I can feather the low side, can't the high side. I lose the reverse which is handy in this clay when it bogs everything down.
So I'd say yes, that your machine would operate the auger motor at ten gpm. It just wouldn't be able to move real fast. Of course in your rock situation that wouldn't be a negative at all.
Walter, if your JD has an FEL you might seriously consider the Belltec FEL mounted hydraulic auger system. I have a bud that has one on a Ford construction tractor. He loves it because he can grab a scoop of wet sand or bags of portland cement and he now has some killer down pressure in rock.
I know Don, but you never asked...............
The FEL option also allows him to put the auger in places he'd have more trouble getting the three point to.