I'll try to give you all the details, so this may take a minute...

I installed a power steering pump on a '08 Ram 2500 (42000 miles on it) for a guy. It was a remanufactured unit, and ended up having a crack in the back housing. There are NO power steering units available for this truck, I must have gotten lucky when I ordered the one I had. I ended up replacing the back plate with the one from my core, it was an exact match, good gasket. Installed it, no leaks, no noise no problems. the guy put about 400 miles on the truck last week and backed a trailer into his driveway yesterday and the truck wouldn't steer left. I went to his home and looked in the resivor- BLACK and shiny metal. My first thought was I screwed up by putting the old backing plate on, so I took the power steering pump off and tore it down. The vanes are perfect, no scratches, shaft is tight. Re-install the pump, flush the system. In the air- turns right just like it should, turning left was a bit harder. I did the whole 40 left to right turns, re-drained the resivor and it was clean, re-fill, set it on the ground and turns right just great, wont turn left.
I should probly sleep on this before posting (been out in the sun rolling around on gravel for the past 6 hours) but I'll get your opinions. I'm thinking gearbox, and I did find a recall notice for steering, but it was for the clamps and he has had that one done, there is another recall for drag link but I haven't bothered the poor old guy to find out if he has had that one taken care of. Im my mind, the pump pumps one way, if it's turning right just fine then the pump is doing its job, no leaking, no screaming, just pumping. There has to be something physically restricting the turn to the left.
Thanks,

 

I would say a piece from the failed pump has found its' way into the control valve of the steering box and blocked a passage or damaged a seal.

 

That sounds about right.

 

Agreed. Because the PS pump itself wont control what direction the wheel go. But if there is no binding in the front end components itself, then the issue is now in the R&P or gear box as said above.

 

Sorry it took me so long to let ya'all know what happened.
The gearbox was bad, thinking back on it, it was most likely the gear box contaminating the PS fluid in the first place. I replaced the gearbox, flushed the system untill I was positive it was clean (about 8 quarts of ATF+4). Went down the road like a slalom racer, and did my best to test it thoroughly. Everything is back in working order.
During my research I found out that the PS pumps on that particular truck is no longer available, not through Napa, O'Reily, Carquest, AutoZone, the guy down the road, or Dodge. There is a replacement PS pump available from Dodge, but at a price of 700 bucks (including resivior, pump, brackets). The gear box is the same. "Not Available".
After questioning the guy a little more, the initial problem was simply whining from the pump. He was convinced that the dealership did something wrong when he took it in and they told him that the parts were backordered, and dumped some conditioner in the system.
All in all, I lost a few bucks on that job. But, now I know.

Ohh, and he was so mad at the local dealership (for not working with him on his 40k truck) that he traded it off. Must be nice.