The ticking is air in steering system, pump, gearbox. Purge the steering system of the air, and it will go away. Gearboxes, many have a screw cap in upper part of the gearbox, on the side, somewhere close to steering column. Unscrew the cap, use suitable thread barb, connect vinyl tubing to the barb, the other end of the tubing put in the top off reservoir. This creates loop. Start the truck, and fluid will circulate through tubing, and into the top off reservoir, this will purge any air, and the ticking will end. I experienced all this ticking thing in the steering, and this was the fix, purge the air from steering system. Why the air causes ticking?
Air causes CAVITATION, and this is why ticking.
I experienced this on GMC T7500 GVWR 33000 lbs, class 7 truck, it has wabco airbrake compressor, steering pump attaches to the compressor and is gear driven set up