Nissan patrols have always been known for having steering problems throughout the years, in recent years there has been much improvement s in caster correction.
With the development of caster plates in the early days then there was drop box's, drop radius arms and now the latest is the Super Flex Arm.

But for now let’s talk about why caster correction is needed.

Manufactures set their caster correction from factory to suit a standard height lift that the 4wd is designed for, as we lift the vehicle the caster reading will change due to the radius arm being connected only on one end to the vehicle so this make the radius arm rotate as the car becomes higher of the ground.
Common problems associated with incorrect caster is the more you lift a Nissan without correcting the caster the vehicle will wander more on the road following all the imperfections on the road surface.
If you put too much caster correction in the vehicle without the needed lift it will create what we refer to as “head shake” which is an extremely dangerous situation that when it occurs it could cause the vehicle to crash.

What we have found at superior engineering is that tire size has a huge difference on how much caster correction is needed.
The larger the tires fitted to the vehicle means you will not need to correct the caster as much.
If you use a 37 inch tire with a 6 inch lift you do not need to use a 6 inch drop box or radius arm but rather use a 4-5 inch drop box / radius arm, as they will drive better, this is to do with the angle of the king pin in relation to an imaginary verticle line and the contact patch becoming larger as the tire size increases.
The best way to understand this and what caster correction is needed is to talk to someone like Superior Engineering who deals with this every day, they can recommend the best solution.
 Drop boxes are the best overall option for most Patrols that are mainly driven on the street as well as occasional off-road use.
They come in 2 different sizes, the 4-5 inch lift and the 6-7 inch lifts.

Except for drop box’s all the other caster correction works by rotating the diff only, drop boxes work the opposite way by dropping the rear of the radius arm down approximately the same amount as what the vehicle is lifted above standard.

Excluding drop boxes, caster correction such as caster plates tend to allow a percentage of the impact encountered when driving to transfer up the radius arm and into the chassis, this means the shocks and coils do not work as much.
The problem is the ride is much harsher than when a drop box is fitted.
When a drop box is fitted ,the radius arm is dropped down at the rear so it is now supported in a more horizontal line behind the front diff, this than enables the shock and coil to do their job properly , this reduces the harsh ride and will create a soft ride.

The one down fall the drop boxes have is they do lose ground clearance but for a mainly road driven vehicle this is not a concern to most.

Now we will discuss how to fit Superior drop boxes to your vehicle.

Step 1.
Place your vehicle on a hoist and remove the front wheels, if you do not have a hoist you can support the vehicle on the properly rated vehicle stands under the chassis but make sure you put the hand brake on.
It is recommended to remove the front panhard rod as well as the coils; this will enable you to lift the diff up further to assist in fitting the radius arms later.
Leave your shocks connected for safety.
Remove the tie rod (the steering rod behind the diff)

(image001)

Step 2.
Remove the factory sway bar and link pins, drop boxes can still use your sway bar if you like but you will need to fit extension or disconnects to it.
It is recomended to use a gearbox stand under the diff to adjust the height of the diff as needed.
Now remove the radius arm from both sides .

(image002)

Step 3 .
Using a marker pen or engineers chalk mark a rectangle on the underside of the chassis where the radius arm connects into, the size is 80mm wide 65mm back.
Now carefully cut this out on both sides with a 4 or 5 inch grinder, it is best to use this cut off wheels.
Be careful not to cut the original radius arm boss.
Clean up the area and paint the bare steel for anti corrosion purposes.
This is not structural and many engineers pass this modification.

(image003)

Step 4.
Now place the steel machined boss that is supplied in the kit into the original radius arm hole from the rear forwards, it should end up approx flush with the front face of the chassis boss where the radius arm was fitted. It is recommended to put some grease in the hole and around the boss to stop any corrosion.
We use this design so the drop box is supported as close as possible to the chassis and it does not put any additional strain on the chassis.

(image 004)

step 5.
Support the transfer case and remove the gearbox crossmember bolts from one side only, loosen the other side crossmember bolts so you get approx 20mm gap between the chassis and the crossmember.

Step6.
Slide the drop box into place from the front backwards; place the 16mm high tensile bolt through the drop box and into the steel boss previously installed.
Place the 4 crossmember bolts back in and loosely tighten.
Duplicate this procedure to the other side but do not tighten any bolts until both sides are installed.
Once they are installed the top bolt that goes into the chassis must be tightened first to pull the drop box backwards, the 16mm bolt should be tightened to 215nm or 161ft/lbs.
Once those are tight proceed to tighten the 8 crossmember bolts to 150nm or 112ft/lbs

(image 005)

Step 6.
It is normal for a small gap to exist between the chassis at the front of the drop box as the factory chassis is slightly curved and the drop boxes are manufactured straight, there is no compromise is structural safety of the drop box or chassis.
Now that the drop box is in place and secured properly it is time to replace the radius arms.
First we must cut the factory washers for clearance in the drop boxes.
As Superior Engineering has the lowest slimline drop boxes available you need to make some clearance for the washers to fit in.

If you do not want to cut your washers you can fit them without cutting them but we recommend cutting the washers.
As pictured in (image006) a small amount of the washer needs to be cut from one side only, it is best to use a vise and a 4 inch grinder, clean any sharp edges off.

(image006)

Step 7.
You must check that you have standard radius arm bushes and not caster bushes in the front of the radius arms, this can be done by looking at the bush and a factory bush has the hole in the centre not offset, also check there is no tears or it is highly recommend that you change the bushes prior to fitting the radius arms.
The easiest way to fit the radius arms is to raise the diff up high to give you enough clearance under the diff to push the radius arm into the drop box, do not use oil or grease on the bushes.
Once the diff is raised enough place one modified washer with the cut end upwards and a new Mushroom bush onto the radius arm, the other bush goes in the drop box  from the rear ( it is recommended to replace the bushes while it is apart) , next push on the other washer with the cut facing upwards with the nut last.
Now push the front of the radius arm into the diff mounts, you may need to rotate the diff slightly to get the bolts in place.
Duplicate this on the other side.
Tighten all the radius arm bolts and nuts to the factory torque setting.

(image 007)