Hi, first post here. My truck is 2007 2500 Cummins with 4.5" lift and 35/12.50/17 tires. Been looking but haven't quite found what my steering is doing.
first, just replaced the steering gear box with a Napa special rebuilt, flushed, the system also. Seemed to tighten up decently, and I put maybe one trip to town on it (60mi). Got home and swapped from the toyos that have been on it for 35k to a set of BFG KO2
In the same size on different wheels.
Now starts issues... Put another 100mi on with no problems, but now steering is getting wierd. Steering wheel is going back to center with more pull then it should, kind of "tugging" back to centerline. Going down the hwy is fine, but off in the curves it's irritating.
Could it be valving in the rebuilt box? Pump? Alignment? Don't think it's front u joints because it gets worse at hwy speed & they're pretty fresh but maybe?
I flushed the system again for good measure tonight and didn't feel any difference. Going to swap tires back tomorrow to try that, but it doesn't feel like it's in the tires because it does it at almost any speed.

 

I have never had luck with a Napa gear box. I've always had to replace within a few days. Disconnect pitman arm and check if still binding. I would get my money back and get factory gear box. The sector gear adjuster would always come loose even with their locknut installed.

 

Yeah I think I'm just going to change the Box Saturday or Sunday, I went and drove it today and I really think that something is off in the Box. It's steers way way too easy with almost no feedback until it starts to give the weird pull back to Center.
I think it's actually less work to change the steering box then to swap tires again.

 

Could a bad steering damper cause that?

 

Checking alignment is really easy by jacking the truck off the ground with stands and using construction string running around the truck. Its not perfect but you will certainly get an understanding if something is out of wack. You can also use measuring tape and and string between the rims to verify distances too. Youtube is good for reference videos on how to do this.
Aside from looking for bent of loose steering/suspension components which will always affect how the vehicle drives, you must assure that the toe setting is not too parallel or toed out otherwise tires will wander. A very slight toe in is necessary for tracking.

That said, caster will play a big part in wander and pull. Cross caster is built in the axle to help ride towards the road crown, but the more you lift the front suspension the more the caster moves in the negative direction. You can adjust it out but at some point the factory control arms are simply tapped out and you need aftermarket ones with more caster adjustment to get the setting back in the positive direction. Note: positive caster is way better for friendly steering characteristics.

Then tires will also play a part in pulling. There's even a saying coined "Toyo pull" because how notorious the Toyo M/T's are for causing a pull. So point being is large tire that are worn will always want to run where they want and might pull the steering. Swapping tires around should help understand if the tires are the problem.

 

I've great luck with red Head steering boxes.