Steering slips

Your description can apply to a number of different symptoms, but the most common cause is a loose rack and pinion steering gear. It can't fall off and except for very unusual circumstances will not become disconnected resulting in a total loss of steering control, but it will cause unpredictable steering response.

The people at a tire and alignment shop will be able to identify this by watching the steering gear while another person turns the steering wheel back and forth with the engine not running. What you will notice is the steering wheel will be in different positions when you're driving straight ahead. This will not cause a pull or a change in alignment / tire wear. You might be able to hear the steering gear make a rumbling or thumping noise as it shifts position if you turn the steering wheel left and right a half turn each way while the engine is off. It will do that too with the engine running. It's just easier to hear with the engine off.

There are other possible causes that WILL cause a pull to one side when you let go of the steering wheel, as well as the off-center steering wheel. One cause is a badly worn front strut. You should hear a knocking noise with that too. You'll have greatly reduced steering control, but again, not a total loss of control.

A worn lower ball joint is less likely to cause this because the changes in alignment it causes aren't usually enough to make the steering wheel shift position enough to notice. Those will be inspected too by the mechanic. A worn ball joint IS a serious safety issue because if one of them separates, that wheel will squirt out on the bottom and you'll just be going along for the ride until the car skids to a stop or hits something, ... Uhm, ... And skids to a stop. That will usually cause body damage too to the fender.

Other things to consider are badly worn upper strut mounts and deteriorated control arm bushings. Inspecting both of those are more involved and are often overlooked. Control arm bushings don't cause a big change in steering wheel position, but they cause a huge change in the alignment, and therefore bad tire wear patterns. Struts have to be removed and disassembled so the upper mounts can be inspected for normal wear requiring replacement, so the mechanic usually doesn't know you need them until he has started on the typical maintenance strut replacement procedure. We hate having to tell you more parts are needed once we've given you an estimate and the job has been started, but sometimes we have no choice. If an upper mount is very badly worn, there is usually some sign such as rust around the larger center nut, or we can see the nut move around while a helper turns the steering wheel.

Yup. This is still typical of a loose rack and pinion steering gear. The fix is to shove it to its proper position, then tighten the mounting bolts.

There's two possibilities. The mounting bolts are loose or two rubber mounting bushings are very badly deteriorated. Every rack and pinion steering gear I've seen has a solid metal-to-metal mount on the driver's side, and most have a rubber bushing sandwiched inside a metal bracket on the passenger side. For the gear to slide back and forth, the mounting bolts have to be loose on the driver's side, at a minimum.

This all assumes my guess is right. You have to look down from on top or crawl underneath, and watch while someone works the steering wheel. If you can't get your eyes in there, or you don't know what to look for, have the car inspected at a tire and alignment shop. They specialize in finding the causes of things like this.