Truck is a 2006 2500 with a 5.9 cummins about 120K miles

On the road there are no problems. But off road on rocky stuff there is an obvious feel and clunking sound in the wheel. Talked to the shop where I bought the truck, they thought it was ball joints and checked them but they were fine. So now it is getting worse. There seems to be a tiny amount of play at both ends of the steering gear. How much play is normal? I hate to just buy parts if they are not needed.
Everything else is solid with no play.