UP FRONT, THE XJ USED THE FIRST VARIATION OF THE COIL SPRING SUSPENSION THAT LATER GRACED THE GRAND CHEROKEE AND WRANGLER TJ. IN BACK, LONG, SUPPLE, FAMILIAR LEAF SPRINGS WERE USED. DESPITE THE DISSIMILAR SYSTEMS, THE XJ IS ACTUALLY QUITE BALANCED AND RESPONDS WELL TO LIFTS, USUALLY WITH FEWER SIDE EFFECTS THAN THE ALL-COIL JEEPS.
As mentioned in part one, the XJ has pintsized wheelwells. Large tires require lot of lift to fit, so it's fortunate that the Cherokee is fairly forgiving in the suspension department. Just be sure you're cool with mounting that long-legged horse after a big lift! Some people need steps!
Front Suspension
Short-arm with drop brackets and long arm. The "short" and "long" refers to the length of the lower control arm, the short being near to stock length. Short arm lifts are viable to about four inches of lift, after which strange things begin to happen due to increased angularity on the arms. When you add drop brackets to a short arm lift, you reduce the angularity, allowing the arms to remain close to the stock position. Long arms are the ultimate in lift height, installation complexity and cost, but also in performance and, usually, ride quality.
Staying in the short arm category, lifting can be done several ways. The first option is spacers. A spacer is installed between the top of the coil and the upper spring seat. They come in polyurethane, metal or as an adjustable unit. These are best limited to about 2 inches of lift, because above that it becomes difficult to correct suspension geometry. Besides reducing castor, the axle also moves backwards and this can complicate tire fit. Plus the lower spring seat gets tilted and leads to bowed springs and bump stops that miss the place they're supposed to bump against. It can also interfere with the track bar's free travel.
Spacers usually come in 1-2 inch thicknesses and can also be used for corrections to ride height in combination with other lifts. This often comes into play when a winch is added, the weight of which drops the front ride height. Ditto for engine swaps or anything else that adds weight to the vehicle.
Next up are spring lifts, which are basically taller coils. Without a longer lower arm, or an adjustable one, a coil-only lift has the same problems as noted above. Lifts above two inches usually come with new lower control arms that at least partially correct the geometry and axle position problems noted above. The arms also have a bow near the lower connection, which avoids interference with the axle mounting bracket when the suspension droops.
At four inches of lift, the problems with short arms become extreme. The main issue is the angle of the lower control arm. When operated at a steep angle, even when corrected somewhat by a longer lower arm, road vibration and shock loads are transmitted up and back instead of in a fore-and-aft direction as the designers intended. Besides a rougher ride, this can lead to early bushing failure and even mount failure if the XJ is used hard. It also leads to rapid changes in suspension geometry with ride height changes, such as when the vehicle leans in a turn.
There's another adverse symptom that occurs with short arm lifts that are above the "magic" four inches, especially if allowed too much wheel travel. When the wheel encounters a rock face or ledge while the suspension is drooped, it tends to push the axle even farther back. Damaged components are the result if the driver tries to "force" the vehicle up by applying power. Having an engaged locker up front will help because the tire will pull itself ahead and resist the tendency to roll under.
A short arm lift that has dropped control arm chassis mounting points eliminates most of the problems noted above, but it adds to the complexity and expense of the kit. The results are great, however, in all departments. Anything you can do to get, or keep, the lower arms close to horizontal is a good step.
Long arm kits are the ones that offer the mega lifts combined with very few downsides... except to your wallet. Basically, the lower arm is extended to mount farther back on the chassis. Special mounts, often combined with a new skid plate/t-case mount, are attached to the chassis. How they are attached to the unibody is a vital consideration. Many times, the OE upper mounting points are retained with new arms but sometimes they are relocated. Sometimes a radius system is used, which eliminates the upper arms altogether, replacing them with single arms that attach to two points on the axle via a "Y" type yoke.
The track bar is worth a few words on it's own since it's used in both short and long arm lifts. If you lift the Jeep over about 2 inches without either installing a longer track bar (or an adjustable length bar) or a relocation bracket, the axle will be pulled towards the driver's side because the eye to eye distance between the track bar mounts decreases with lift. Most kits at or above three inches have one of these "fixes", but those of you that mix and match parts to build your own budget lifts will have to add a track bar remedy to your list.
Finally, here's a tip that will help in the NVH department. Make sure the kit you choose has rubber in a least one end of the replacement suspension control arms. Because the XJ is a unibody vehicle, NVH is more easily transmitted to the passenger compartment from the suspension. While polyurethane is more durable than rubber, it tends to transmit more NVH. It's worse if the angularity of the arm increases. The suspension kit manufacturers have learned this and typically offer kits with a rubber bushing at the chassis end.
You can only drop a Pitman arm so far before it puts too much strain on the steering box, so in case of a great deal of lift, you may need to go to a modified, "Hi-Steer" type steering setup that moves the mounting points of the tie rod and drag links above the knuckle. It's an expensive cure, but necessary in some cases.
Rear Suspension
The rear leafs are the XJ's saving grace in the lifted-Jeep manners department. Many of the worst drivability symptoms noted by full-coilers come from the rear suspension. The XJ's leaves avoid these problems and as a result, they do not experience the jacking and roll-steer a lifted TJ or ZJ may suffer.
Lifting the rear is easy. At level one are lift blocks placed between the spring and axle. This has the advantages of maintaining stock ride quality, easy installation and low cost. The downside is that axle wrap is more likely and it may make for a less than desirable driveshaft and pinion angle without the use of tapered axle shims. Lift blocks to about two inches produce few problems.
Another level one rear lift method is the use of add-a-leafs. These consist of a single leaf that is added to the existing spring pack to increase the spring's rate and arch. These typically offer up to a 2-inch lift without any danger of axle wrap. Again, they are inexpensive and easy to install. On the downside, they will decrease ride quality and may reduce articulation. As with the lift block, tapered axle wedges can be used to correct pinion angle.
A longer shackle will also lift the rear, but only by half the amount of the increase over the stock shackle's length. If the shackle is two inches longer than stock, you will get one inch of lift. On the upside, that will also tilt the pinion up. On the downside, a longer shackle on a stock spring will change the shackle angle adversely, bringing it closer to vertical. You want to keep the shackle angle a bit past vertical, with the lower eye tilted back for the best ride.
Spring lifts are the best option. An increase in the arch of the spring combined with longer shackles works very well. Longer shackles are often needed because as the spring compresses and gets flatter, its eye to eye distance increases. A short shackle will soon run out of travel and you will have to limit uptravel at that point or risk breakage. In most cases, this isn't a worry on an XJ. The tire will run out of room for uptravel long before the shackle runs out of travel. The kit maker should have this figured out by including the right shackles as needed and a bumpstop lowering device to stop uptravel at the right time.
Sway Bars
Sway bars are what make your built rig safe on the street, so don't consider removing them. Yes, they do restrict wheel travel on the trail but with the availability of sway bar disconnects, you can have the best of both worlds. If the kit you buy does not include them, they are a worthwhile supplemental purchase.
Steering
With lots of lift, steering problems may become an issue. Bump-steer is the most common malady. Bump steer is when up or down axle movement causes unwanted steering input. This includes wandering or, in the worst cases, rapid darting to one side or the other. If you keep one important element in mind, steering problems associated with lifts are minimized. Make the necessary mods to keep the drag link and track bar at the same angles. Overall, the less angularity on either of these components the better, but you can only do so much.
On the trail, with lots of suspension movement, bump steer is impossible to avoid. It doesn't really matter usually, because you're going 0.25 mph and you can correct for it. It's those first few inches of travel above and below normal ride height that are the important ones for street driving.
Another problem that may occur with the taller lifts is that at the increased angles, the tie rod ends on the drag link may be closer to their binding points. If the suspension drops enough to bind them, they may break or bend the rod. The stock components are on the weak side for tires above 31 inches. Several companies make super-duty steering systems that incorporate rod ends that can handle more angularity, as well as stronger rods. If angularity isn't the major problem, a cheap wrecking yard upgrade is to find a Grand Cherokee ZJ V8 tie rod, which is stronger.
The first element in steering geometry correction usually comes in the form of a dropped Pitman arm. This lowers the steering box end of the drag link, reducing the angle and the effect suspension travel has on the steering. The amount of drop will be appropriate to the lift, but the available drops run from 1-4 inches. Bear in mind the importance of keeping the drag link and track rod parallel.
Lifted XJs should all be equipped with a steering box reinforcement plate and/or a brace. The plate beefs up the unibody mounting area the box bolts to. The brace secures it laterally. The usual advice is to install one or both with tires of 31 inches or above. Tearing the steering box loose from a full chassis rig is rough enough, but on a unibody XJ that repair is an extensive one. Add the cost of a plate or brace to your XJ budget now!
Shocks
Shocks are usually included in a lift kit. Sometimes a better shock is optional. The first important element is that the open and closed lengths of the shock match the suspension's travel. That's something the lift manufacturer should have figured out for you already. The actual type of shock that's best for you depends on your 'wheeling.
Mild 'wheelers and slow movers, which includes a lot of rock crawlers, can get by fine with an ordinary hydraulic, low pressure gas, or cellular gas shock. That doesn't mean you can't upgrade to something more expensive, but generally you are best off to avoid high pressure shocks for a good ride and free articulation.
Fast movers are best off with high pressure gas or remote reservoir shocks. The shocks on a fast mover's Jeep are working hard and generating lots of heat. Heat makes the oil foam and reduces the shock's effectiveness. The high pressure gas stalls the overheating point somewhat. Fast movers can also benefit from dual shocks, which are valved to provide the same effect as a single shock but will share the heat load. Today's shocks are so good that seldom are duals needed for the non-Baja Racer types.
Driveshaft Angles
Driveshaft angles will increase with lift. Not addressing this issue results in vibration and short u-joint life. Lifted vehicles may also need longer driveshafts. In day-to-day use, if your u-joint is operating at anywhere near 15 degrees, it will wear out very quickly. If it gets near 30 degrees while flexing on the trail, it may bind and break. Getting the rear shaft in line can be hard enough at times, but getting both optimized can get difficult. This problem is complicated in the XJ because of its live hub front axle design, which has no locking hubs. If you have a limited slip or automatic locker up front, your driveshaft will be spinning all the time, even if no power is applied. If the front driveshaft is not properly set up, it will vibrate.
The answer for the back driveshaft is relatively easy. For mild lifts, you won't have maximum angle problems. You will usually just need tapered wedges under the springs to match the pinion and t-case rear output angles to avoid vibration. Nearing three inches of lift, you may need a slip yoke type CV driveshaft and a pinion angle adjusted to parallel with the driveshaft. Above three inches, a fixed-yoke, short shaft conversion to the transfer case, with a CV driveshaft, will be the best way to keep the rear 'shaft bind and vibration free.
Up front, you have a similar problem and a similar answer. The t-case already has a fixed yoke and a CV joint (the '84- 86 GKN type is junk and MUST be replaced), but correcting the pinion angle becomes the problem. With adjustable arms you can set the pinion angle to match the driveshaft, but you lose castor. While castor is important to straightline tracking, it's less important the bigger the tire you run. If faced with the choice of getting the pinion angle right or castor, most times the driveshaft takes precedence because the big tires will take care of the castor issue.
In some kits, you may be offered a tcase lowering kit. Seldom do these provide optimal results. While they are sometimes enough to alleviate the worst symptoms, it's often a case of fixing one end, while making the other worse and having to live with a vibration. Installing a locking front hub conversion will make front driveline issues easier because you can lock out the front axle and then an imperfectly set up front driveline isn't a huge issue. Bottom line, if you plan an extensive lift, budget CV driveshafts and a t-case rear output kit from the get-go. The results are always better.
CAPTIONS
One of the most critical elements to an XJ lift is matching the drag link angle with the track rod. You can see this one is a little off. The result might be more bumpsteer, or worse bumpsteer. Note also that the rod ends on the drag link are close to being maxed. In a situation where the right front is fully drooped, these rod ends could be bound and popped apart.
A typical lift kit of about three inches showing the angle of the lower control arm. Line three is the approximate chassis level. Line 2 is the angle of the lifted arm and line one shows the approximate angle of a stock arm. Note how the axle end of the arm is bent. That's to clear the spring perch/shock bracket indicated by the arrow
This steering box mounting area has already suffered some damage and has been repaired with a rather nastily welded-on plate that should do the job. Don't wait to suffer damage before you buy a reinforcement plate. Note also the dropped Pitman arm.
A shackle four inches longer than a stock shackle will provide two inches of lift.
A lift block is a viable and inexpensive way to lift the rear of a Cherokee for a mild 'wheeler with 31s or so. Bigger tires, harder terrain and lower gears will make the tendency for spring wrap worse, so at or above three inches of lift, you are best off with new springs.
The XJ can flex! You can easily get more flex out of the rear than the front. That tends to make for an unstable vehicle. Better to have articulation evenly balanced front to rear, or at least 40 percent front/60 percent rear. A Rubicon Express long arm kit makes articulation balance easy.
The Rubicon Express 7.5-inch longarm front suspension. Note how the arm is relatively flat, meaning there will be few adverse street symptoms. This is a radius arm setup with a separate upper arm that locates back to the main arm. This upper arm keeps the axle from rotating. It's adjustable so that pinion angle and castor can be set at ride height. Note the serious long-travel remote reservoir shocks. The pressure in these can be adjusted to suit the driving situation. Note also that this rig has a Dana 44 front axle conversion.
Here is a Rubicon Express 5.5-inch rear leaf with a boomerang shackle. This is a very flexy spring, with space over the bolt clips (red arrows) for the spring to droop down. It also has a boomerang type shackle (blue arrow), which allows the spring to flatten out more on compression without having to be excessively long.
