A Nissan specialty shop is not needed for front suspsension work on the 720. It's a std design.
Slop in the ball joints can be tested on the 720 by jacking under the lower control arm as close to the tire as possible. This takes the spring load off the ball joints: the jack pushes on the control arm, the arm pushes the spring, the spring lifts the truck via the top end of the crossmember or frame (I forget which, and I'm too lazy to walk outside and look). You cannot just jack up the truck anywhere to do a ball joint check, you
must jack almost directly under the spring, or as far outboard as possible. That is the only way to unload the ball joints.
Then grasp the tire at 6 o'clock and 12 o'clock, push with one hand and pull with the other, then switch directions and pull/push. You will feel the tire/rim shift when you do this. Some of the movement is normal: wheel brg play. It's best to have a second person do the push/pull whilst you lay down low from the front and watch the spindle/balljoint relationship. If the wheel/tire moves but the spindle does not, the ball joints are not sloppy (though they could be seized). If the spindle moves too, you can see which ball joint is allowing the movement.
Constant pull to one side: check brakes first (dragging caliper, rusty caliper slides). Next, rotate the front tires
side to side. Members Clay and Caxambu have both found bad tires causing their pull (I have seen over a dozen over the years). If brakes and tires are ruled out, caster may be off on one side, usually the result of wear in the control arm bushings or a collision that changed the relationship of the mounting points (or sometimes a bent lower control arm).
On the 720, the idler arm is "always" bad (loose bushings). See
this thread for details.
Tie rod ends and steering box check: bad tie rod ends won't cause a pull, but will cause excessive tire wear and a lot of lost movement in the system, symptom is having to move the steering wheel a lot back and forth to keep it aimed down the road -- masked by your pull, in your case. With tires on the ground, engine off (except Chrysler w/PS), get a helper to use
two fingers to move the steering wheel constantly one direction and then another. Move the wheel just until it's too hard to turn with two fingers, then switch directions and go the other way. Frequency of about one change of direction per second (0.5 Hz). You do not want to actually move the tires, you only want to load or move everything up to the spindles. Then you lay on ground and watch the entire linkage, starting at the steering box. The arm coming off the box is called the Pitman arm. You can see the box's input shaft (the rag coupling) as it moves back and forth. How far does the rag coupling move before the pitman arm begins to move? If "a lot", you may have a worn steering box. On the 720,
some of the box's internal wear can be compensated by an external worm gear/sector shaft lash adjusting screw. You can easily overadjust it and cause the box to lock up when it's turned to either extreme, so be very careful playing with that. See
this thread for more info. Philip & I had a good post on this topic elsewhere, but I apparently didn't copy it over to this site: one big reason I left there was due to the lack of a Search facility! (Philip: do you want to try to find it over there? Probably Aug-2004 or so.).
If you wanted to go through the whole front suspension, you'd touch:
- Idler arm (or idler arm bushings)
- Tie rod ends (outers)
- Center link (which contains the inner tie rod ends: these rarely go bad on the 720)
- Upper A-arm bushings (two per side)
- Lower control arm bushings (inners)
- Radius arm bushings (frequently bad/rotted, but very cheap to replace)
- Upper & Lower ball joints
If you pay someone else to replace all of that, I would expect the bill to run $600-800. The idler arm alone is $100. Alignments run $30-80, depending on the shop. But it's unlikely you need the whole shebang replaced, and I would only go that route if you were in a special situation.
IMO, the idler arm (bushings) is the most common problem. The outer tie rod ends are reasonably durable, and a lot of them are greaseable, as are the ball joints -- grease them periodically to flush out the dirt.
If you replace the idler arm or adjust the steering box gear lash, no alignment is
necessary. If you touch anything else, you have to have it aligned -- and no reputable alignment shop will align a rig with any worn parts (it can't really be done, and besides parts replacement is how alignment shops make a living -- it's not on the profit in the alignment, which is nearly a give-away).