There's two types of steering systems. Rack and pinion systems don't use many other parts. Your system uses a steering gear box with a "pitman" arm. That attaches to a center link that has other linkages attached to it. The other end of that center link is held in place by the idler arm. It's bolted to the frame, and the end of the arm has a tapered stud that can rotate. Separating that tapered stud is the hardest part of the job. Many auto parts stores borrow or rent tools to do that.
Some idler arms are adjustable. You start by measuring the height of the tapered stud, then you bolt the new arm on so it is at the same height. Next you either measure its height and compare it to the pitman arm or you can use a level to insure the center link is perfectly level. The geometry of the steering linkage must match the geometry of the suspension system for proper handling.
The new idler arm will put the end of the center link back in its correct orientation where it was before the old one wore out but it's still a good idea to have the vehicle aligned. If you push and pull the old arm up and down you will see the right wheel turn left and right a little. That wheel movement is called "toe" and is critical for good tire wear.
March, 30, 2013 AT 8:15 PM
One idler arm. Costs about $40 at autozone, advance auto, etc,
You will need to have your front-end aligned after the idler arm is installed.