Front Suspension Popping
Oh, that sagging front end (torsion bars)
Front Suspension Popping (Paul Hagan) Popping noises in the front suspension could be caused by under-torqued or loose lower link-to-frame bolts -- click here to read the full article by Paul Hagan.
Alignment Caveats (Martin Chung)
Problems related to alignment are pretty noticeable: tire wear, wandering, bad steering feel, etc. This is especially so if a lift kit is installed. However, one thing to make sure of when taking your vehicle in for an alignment is to make sure the shop does check all of the alignment parameters.
The three alignment parameters on the Nissan front suspension are camber, toe, and caster. Camber is the amount that the tire tips inward or outwards from the wheelwell (negative camber is when the tops of the tires are closer to the body than the bottoms -- think of the old VW Beetle rear tires when thinking negative camber). Toe-in is the amount that the fronts of the tires turn inwards towards each other (like pointing your own feet inward towards each other, pigeon-toe fashion). Finally, caster is the amount that the contact patch of the tire is offset from the geometric axis of the suspension (supermarket shopping cart front wheels or chair rollers/casters exhibit caster).
The factory settings for the Nissan trucks typically call for a small amount of toe-in. Toe-in can counteract the tendencies for the tires to toe-out under acceleration. Very little camber is called for, so the tires should be nearly perpendicular to the ground. Finally, a small amount of positive caster provides a bit of self-centering to the steering system (try pushing a shopping cart wheel in reverse, and you'll see that it always flips around to face the right direction -- this is what positive caster will do).
Fair enough, you say, but where's the problem?
The toe-in on the IFS is easy to change by rotating the adjusting sleeves on the tie-rods. The problem is that the camber and caster are only adjustable by loosening or removing the spindle that the suspension upper control arms are attached to. This is a bit of work as it requires removing the tire and two large bolts. It has been my personal experience that some shops may only adjust the toe-in and not bother with the camber and caster. Thus they only do 1/3 of a proper job.
On my last alignment, performed after my lift kit installation, I asked for the before and after printouts. To my disgust, the toe-in was adjusted to zero, and the values for camber and caster were completely unchanged, and they were not within factory spec. In fact, I was running with negative caster on one side. So basically nothing was to factory spec, although they were all close to zero. This was at a shop with computerized alignment machinery, so I wonder if it was the technician or the computer that declared my suspension to be aligned.
So this short article is for anyone planning a suspension alignment -- be sure to verify the proper values for your truck, and insist on getting the before and after values to check what was actually done before you fork over your money. Nissan does charge extra to align Pathfinders, possibly recognizing that slightly more work is involved.
Torsion Bar Adjustment (Martin Chung)
These trucks sag. Over time, the torsion bars wear out and lose their springiness. Luckily, there's an easy fix for this -- you can crank up the torsion bars.
The torsion bars are simply a round bar that is springy when it twists. Attach one end to the frame, and the other end to the A-arm hinge, and it will support the weight of the truck and provide the desired springing action. Each end of the torsion bar is splined to engage into an adjuster (frame side) and a mounting plate (A-arm end).
The adjuster controls the height of the suspension by rotating the torsion bar relative to the truck thereby pushing the A-arm downwards away from the frame. The adjuster mechanism is simple: a bolt, nut, and a locking nut keep the adjuster at the appropriate amount of rotation. The adjuster is secured within one of the frame crossmembers midway under the vehicle.
The stock height (94 4WD trucks) is measured from the lower A-arm bolt (that the A-arm attaches to the frame with) and the steering bumpstop (the small angled bit of metal on the A-arm very close to the tire that hits against the steering angle adjustment nut on the inside of the wheel hub). Measure these distances to the ground.
Bumpstop to ground distance is about 9.5" (31" tires). A-arm bolt to ground distance is about 11" - 11.5". The difference between these two numbers (1.5" - 2.0") gives you your factory ride height. Again, on the 94 4WD trucks, the factory ride height should be between 1.6" and 2.2" on both sides. Note that this figure is independent of the tire size.
To adjust the torsion bars, it is usually a good idea to relieve as much weight as possible from the adjuster, allowing it to turn easier. Therefore, jack up the front of the vehicle so the tires are off the ground, jacking it up also gives you a bit more room to work, too. Don't forget the jackstands.
The torsion bars are the long round bars extending from the front suspension A-arms to the crossmember. If you study the mechanism, you'll see that the adjustment bolt goes through the adjuster and out the other side of the frame crossmember, where its other end is held by a nut. There is a second nut on top of that to prevent it from freely rotating off by itself.
Now, lubricate the bolt head, threads, and nut. This will prevent galling or damage to any of the parts from cutting and wearing into each other. Undo the lock nut. Now, while holding the top nut with a wrench (usually it will stay in place without the wrench), turn the bolt with a socket wrench (19 mm). This will move the adjuster -- the further in it goes, the higher your vehicle will go). Remember, though, that a little goes a long way and the effect of any increment at the adjuster is multiplied at the tires, so you only need to crank it up 1/2 or 1/3 of the desired increase in height. There will be friction in your suspension, so it won't move readily.
Once you're done, secure the top locking nut, and go for a quick drive over some bumps. This will settle the suspension in at the new height. Then recheck your height and adjust the bars as necessary. I suggest that you should take it for an alignment as well because minor changes in height can make a big difference in alignment.
Typically, your ride will be a little stiffer than before. Also, this is a poor man's lift -- you can raise the height to about 0.5" or 1" over stock this way. Any higher, and you will require a new set of A-arms to bring the alignment back into spec.