My grove rt 700b has a toggle switch for the rear steer, the steering wheel turns the front axle. Rear steer is main (crane) hydraulic pumps, front steer has it's own hydraulic pump on the motor. Front steer only works if your rolling, you can't turn the wheel in the cab and turn the front wheels. Throttling up doesn't help, you can here a chatter sound as your turning the steering wheel. Steering wheel doesn't stop when the front wheels stop, you can continue to turn the steering wheel slowly, it just chatters and the front wheels won't turn, unless your rolling. If you are rolling they come around okay, its kind of like driving a old truck with no power steering. Rear steer works fine, bump the switch and it goes either way fine. I'm thinking its either pump or the steering orbital. The front axle just has two hydraulic cylinders tied together, pushing/pulling each way, I can't see them both bypassing (steering is the same either direction). I'm leaning toward the pump being weak- it doesn't put out enough pressure to turn the front wheels, so you can continue to turn the steering wheel, the chatter is the fluid dead heading on the steer cylinders, but not pushing them. I suppose I could put it on jacks, if the chatter stays the same with no weight on the front, its orbital, if the wheels move easy with no chatter, its weak pressure from the pump?
I don't know on those rt700's if the use the same pump setup as the older groves like the rt740, rt745. On those there's an adapter that's terrible about wearing out. I have had the same problem and it was caused by the pump splines slipping under pressure. It did that for a while untill it just quit steering altogether. Also this part isn't in any of groves parts manuals that I can find. Grove had no record of this so this on got a set screw. I always make a habit to check these and I've yet to set that had very much life left. Like I say I don't know if the rt700 is different but I'd check into the pump drive.
The rt700b has a 5.9 cummins and the power steering pump is mounted directly on the left side of the motor, right on the gear train set up. Right below where the injector pump sets. Pump mounts like this, but my pump is a little larger. Pulls oil right from the hyd. tank. Pulled this picture from google, but this should just be direct gear drive, no coupler.
Steering issues on the back burner for right now, this morning had a big puddle of oil under the swivel. Moved the crane off the trailer and the steady drip went away, but I think a reseal is in order.
I did call Grove- seal kit with wear ring/ bushings $600, new complete barrel, and spool assembly was $19,000 with a 8- week lead time. I may have to iduchov's route and make a barrel if mine looks bad.
If you have a good hydro shop they can make you a new barrel for the swival. I seen it both ways when you tear the old swivals apart. Some times they are fine some times they are grooved so bad you don't know how they wernt just bypassing the fluid