There's two things to look at for steering wander, plus, if you have a 2500 or 3500 with a diesel engine, there's a 32-page service bulletin to look at for a suddenly-occurring severe brake pull.
If you have a 4wd truck, by far the most common cause of steering wander is a worn track bar. I'm told Napa has a replacement with a lifetime warranty. That is a good deal because this is a high-failure item.
The track bar is attached on the driver's side frame, near the steering gear box, with a ball and socket. On the passenger side it's attached to the axle housing with a rubber bushing. The bar keeps the axle from shifting sideways. Watch that ball and socket while a helper moves the steering wheel back and forth a quarter turn each way about twice per second. If you can see any visible vertical movement between the socket and the stud, replace that bar. Chrysler allowed.080" vertical movement before it was considered worn enough to replace under warranty. They never got that bad because as little as.030" movement was more than enough to cause a steering wander complaint.
That movement can be measured with a dial indicator, but if you can see the movement taking place, you have more than enough wear to cause this problem. That tiny movement allows the axle to shift to one side, then the other, as you're driving. That changes the relationship between the frame and the axle. The steering linkage is also connected between the steering gear on the frame, and the spindles on the axle, so in effect, the linkage needs to change length to accommodate that change. Instead, the wheels turn a little to one side or the other, and that's what causes the wander and constant need to correct the direction of travel.
The second, less-common cause is a worn bushing for the pitman shaft in the steering gear box. The pitman shaft will walk to one side, bottom out, THEN start to turn in response to your turning the steering wheel. You can see this too when your helper turns the steering wheel. Watch that shaft right where it comes out of the bottom / front of the gear box. If you see that shaft move sideways, replace the gear box. If that slop gets bad enough, the shaft will walk far enough away from the lip seal that power steering fluid will drip from it. Do not try to solve this by tightening the adjustment nut. Doing that will cause the gear teeth to bind anywhere near where it is centered. That will make for a very miserable truck to drive because the steering wheel will try to pop away from being centered, and if you try to hold it centered, it will feel tight. Any slight steering movement will be exaggerated
Monday, December 28th, 2015 AT 6:52 PM