The steering is connected to the gear box by a pitman arm on a splined shaft. The pitman arm connects on the other side to a center link using a stud/ball socket, which rides on both the pitman arm and idler arms. This center link has tie rods, and tie rod ends. There are multiple areas that have ball joints and sockets which wear out.

Start my jacking the vehicle up in the front on one end, and shake the tires back and forth. There should be no play in anything. If you're on the driver side you can probably see the pitman arm move (if it's worn out) for yourself, otherwise it's good to have someone else help watch the joints while one person shakes the tires.

Things to check; pitman arm (watch for play in the stud connecting to the center link), idler arm (same as pitman arm), tie rod ends (they are booted ball/socket studs as well, but connect to the wheel spindles), ball joints (both upper and lower, another ball/socket stud design).

Lastly, the gearbox itself can be worn down, and could be tightened in some cases. There's a jam nut and stud on top of the gear box used to tighten it up. Do some research before going this route, you can lock the gearbox up in some cases.

 

Thanks for the info. If its not raining this weekend, I'll dig into some of this.

W/o knowing how many miles are on your truck, how much over-sized your tires are etc, it'll be hard to diagnose it over the internet. However, in my experience these are the parts that wear out - in rough order of what goes out first.

Idler arm - on these trucks the idler arm is actually 2 pieces. The lower piece wears out first. I replaced my lower around 220k. I did not replace my upper idler till ~ 390k miles.
Upper ball joints - Mine were slap-ass wore out when I checked them at around 220k - replaced them then.
Pitman arm - I replaced mine around 250k miles and it was pretty worn out.

As shibby posted, you can check all this stuff easily enough.

Idler arm - I like to jack up just the passenger side front. Grab front right tire at 9 and 3 o'clock and shove back and forth. Watch for the idler arm / center link moving UP and DOWN. It should NOT move up and down. If it does, idler is worn out.
Upper ball joints - put your jack under the lower control arm on one side. Jack it up until the tire clears the ground. Jacking it up like this unloads the springs from the ball joints. Grab the tire at 6 and 12 o'clock and shove it back & forth. Any movement in & out at the top is upper ball joint wear.
Pitman arm - Basically what Shibby said -jack up the driver's side, 3 & 9 o'clock and shove. Watch for any "slack" at the joint between the pitman and the center link.

There's 165XXX miles on the truck. It also has 305/55-20 tires. Thanks for the specifics checking the different parts out.

 

W/o knowing how many miles are on your truck, how much over-sized your tires are etc, it'll be hard to diagnose it over the internet. However, in my experience these are the parts that wear out - in rough order of what goes out first.

Idler arm - on these trucks the idler arm is actually 2 pieces. The lower piece wears out first. I replaced my lower around 220k. I did not replace my upper idler till ~ 390k miles.
Upper ball joints - Mine were slap-ass wore out when I checked them at around 220k - replaced them then.
Pitman arm - I replaced mine around 250k miles and it was pretty worn out.

As shibby posted, you can check all this stuff easily enough.

Idler arm - I like to jack up just the passenger side front. Grab front right tire at 9 and 3 o'clock and shove back and forth. Watch for the idler arm / center link moving UP and DOWN. It should NOT move up and down. If it does, idler is worn out.
Upper ball joints - put your jack under the lower control arm on one side. Jack it up until the tire clears the ground. Jacking it up like this unloads the springs from the ball joints. Grab the tire at 6 and 12 o'clock and shove it back & forth. Any movement in & out at the top is upper ball joint wear.
Pitman arm - Basically what Shibby said -jack up the driver's side, 3 & 9 o'clock and shove. Watch for any "slack" at the joint between the pitman and the center link.

 

With those tires and 165k miles I'm guessing at a minimum you'll need idler and pitman. Wouldn't be surprised if you need upper ball joints too.

 

Admitting I don't know anything about trucks and even less about lifted trucks, how do larger tires increase wear on drivetrain items? Just larger/heavier so more stress or other things too?

 

Think of the larger tire as a torque arm or cheater bar. When you have a really tight bolt you go and grab a longer wrench, right? A larger diameter tire is a longer "wrench" and increases the forces acting on the steering and suspension components and accelerates wear. The weight of the larger tires contributes to suspension wear but probably doesn't affect the steering stuff as much - but some for sure. Offset wheels or spacers for over-size tires are probably the worst as they increase loads and actually introduce a moment onto the wheel bearings. ALL factory wheels - cars, trucks, chevy, ford, toyota, hyundai.... are made to center the load on the center of the wheel bearing. Offsetting them puts a torsional load on the bearings that those bearings were never designed to see. Heck, you don't even have to drive it to do damage to those bearings. Just the 7,500 lb truck sitting in your driveway is putting a torsional load on the wheel bearings that is not there with factory or centered wheels. The farther the offset, the worse the load becomes as torque is calculated as force x length of moment arm. The longer the arm (long wrench), the higher the torque exerted (with the force applied being equal). In this case, the force is the weight of the truck / 4. The forces only grow when you hit potholes or curbs, etc. Those offsets also place additional stress on components like ball joints, control arms, bushings and such.

Having said all that, it's not going to stop people from installing bigger tires. Heck, I run over-size tires on my truck. It came with 245/75 16s and I ran those for the first 207,000 miles. But eventually I got tired of looking at it with those little tires in those HUGE wheel wells so I bumped up the tire size to 265s. They look a lot better and I still didn't need to lift or go to offset wheels.

 

Thats what I figured. Thanks for the details.