Suspension Lift Frequently Asked Questions
(Jan 8/99) - Still working on it, but need help with the Trailmaster section, plus info on body lifts.
General Probably the most commonly asked question about the Nissan W/D21 series of trucks is how to lift them. There are several kits on the market by different manufacturers that can achieve this goal
Control Arm and Torsion bar Lifts (e.g. Rancho, Superlift, Desert Steel)
The Pathfinder and Hardbody trucks have basically identical front suspensions, which are in turn very similar to the 720 front suspension. These are Independent Front Suspension (IFS) systems using double A-arms (or control arms) to locate the wheel, torsion bars for the spring, and shock absorbers.
The A-arms provide for a fixed, limited range of up and down travel. Rubber bumpstops and physical limitations restrict the A-arms from exceeding their travel limits. One end of the torsion bars are attached to the lower control arm; the other end attaches to adjusters located in a frame crossmember.
By adjusting the torsion bars, it is possible to lift the front end of the vehicle. Small lifts (say less than 1") can probably be accommodated this way without needing a lift kit. When you increase the lift, the tires begin to camber negatively (top of tire moves inward towards the body) and the upper ball joint also takes on more of an angle from horizontal. These effect can cause wear on the ball joint as well as take the camber out of the alignment range, causing uneven tire wear.
By lifting this way, the clearance underneath the front skidplate is increased. The drawback is that the front CV joint angles are increased as well. The maximum joint angles are the limiting factor for the amount of lift and have to be a consideration if you want to increase the total travel by lowering the bumpstops. CV joints are weaker at higher operating angles.
Normally, this should not be a big problem as the front joints are only used when in 4WD because of the locking hubs used on the Nissan. In contrast, other makes such as Toyota use a central axle disconnect system in which the front joints are always turning and could therefore wear out faster with the higher operating angles from an A-arm lift.
The remedy for this situation is a replacement upper control arm (UCA) kit. The replacement UCA is longer than the factory UCA to help push out the tire and compensate for the increased negative camber. The ball joint angle is also improved. For lifting the rear to match, the Pathfinder kit comes with taller rear coil springs; the Hardbody kit comes with longer shackles (Superlift) or add-a-leafs (Rancho).
However, by adjusting the torsion bars, one sacrifices downward travel for lift -- basically you are changing the rest or equilibrium position of the suspension so that it is lower down in its travel compared to the stock position. Hence if you lift the truck 2", you lose the 2" of downward travel. The Pathfinder has about 7" of total up and down travel (3.5" each way), so if you lift 2", that means that you have only 1.5" remaining down travel, but have 5.5" upward travel
The physical limit of this lift is of course to lift so high that the upper control arm contacts the bumpstop continuously. This results in a terrible ride because there is no downward travel at all and the suspension is continously bottoming (or is it topping out?). A more practical limit is about 2-2.5" of lift over stock, which provides some room for downward travel that is adequate for street purposes. Thus most kits are listed as 2.5" lifts, though you can run a lower lift if you prefer.
When lifting with the torsion bars, the ride will become stiffer the higher you go. Opinions vary as to why, but the usual one is that the amount of twist, or preload, on the torsion bar increases the higher you go, so you are winding up the spring tighter, so to speak. I've also noted that as you go higher, the tires actually move inwards slightly, thus the springing force has to push against the lateral grip of the tires. The effective lever length of the control arm shortens too, because the control arm forms a greater angle with horizontal. Whatever the reason, the unanimous opinion is that you will notice a stiffer ride.
With regards to suspension alignment, lifting with the torsion bars creates a larger angle with the tie rods, which tends to pull the tires inwards towards the body, causing a toe-in condition (front of tires are closer to the body than the rear of the tires). This is easily fixed at an alignment shop.
The tougher problem is that caster and camber can also change. These are corrected by the alignment shop by adding or subtracting shims behind the upper control arm spindle, which helps to adjust the control arm in relation to the body and the other control arm. The control arms (at least Superlift, in my experience) are constructed so that if you lift a specific amount (around 2"), you will not have to adjust the caster and camber, assuming that your stock suspension was properly aligned to begin with.
In my last alignment, the shop did not bother correcting the camber or caster, only the toe-in. I suspect this is because of the extra work involved with having to remove the tires in order to get to the spindle, or else that my specs were close to spec (they were very close, but not quite perfect). All I know is that I will not be going back to them. You would be well served to make sure that the camber and caster are indeed adjusted. You might have to pay extra to get all three measurements in spec. In fact, my local Nissan dealer charges extra for Pathfinders, which indicates that recognize the additional work required. Make sure you get the before and after specs to make sure the alignment meets factory specifications.
I suspect that some problems reported with lifts such as accelerated or uneven tire wear may be due to the alignment shops and not directly due to the quality of the kits themselves.
Trail Master 4"
The Trail Master 4" lift system is much more involved than the control arm lift. The TM kit includes bracketry to relocate the front differential and lower control arm downwards, plus balljoint spacers for the upper control arm. The mounting point for the torsion bars is also relocated downwards below the level of the frame. The rear lift consists of a coil spring spacer to augment the factory coils.