Please note: I am not a professional mechanic, and this is not intended as a substitute for the manufacturer's instructions. The purpose of these articles is to document my experiences so other XJ owners can decide if they want to tackle similar work.

General Info

The Terra-Flex lift includes spacers for the front and shackles for the rear.
The advantage of longer shackles over AALs (Add-A-Leafs) is that they don't affect spring stiffness and can be added to a spring lift for additional height.
The only disadvantage is that they rotate the rear pinion upward 1.6 degrees and therefore can cause vibrations in the U-joints (usually easy to shim out). I originally thought they would reduce departure angle (compared to A-A-Ls, not to stock), but the shackles match the angle with the bumper, so this is not the case

I bought this lift to put on my 97 XJ, but I got major slip-yoke vibrations from it. The 96+ XJs seem more prone to this due to a design change. I have now mounted the lift in my wife's daily driver 91 XJ, and it will become the trail machine instead of the 97.

Tools

Assorted metric wrenches and sockets, external coil spring compressors, a long flex handle ("breaker bar") for stubborn bolts, a torque wrench, a floor jack, jack stands

Rear

Do the rear first. That way if you only get half done you have your butt end up and not your nose.

1. Loosen upper and lower shackle bolts. If you have a trailer hitch you may need to remove it during the install to get at the shackle bolts.

2. Jack up the rear differential, remove the tires, and place jack stands under the uniframe.

3. Lower the jack until the springs are not compressed and the jack is just barely supporting the weight of the axle. If you have stock length shocks you will need to unbolt them at the bottom for more droop. Make sure you do not over extend the rear brake line.

4. Remove shackle bolts from the springs, then from the frame. Adjust the jack up or down as need be to ensure there is no tension on the shackle.

5. Loosely bolt new shackles to frame using the original bolts (the new ones supplied are the wrong thread). DO NOT COMPLETELY TIGHTEN BOLTS.

6. Loosely bolt springs to new shackles using the new nuts and bolts supplied. Use the jack to line the springs up to the shackles.

7. Replace tires, lower vehicle, and tighten shackle bolts. 80ft. lbs for lower bolts, 115ft. lbs for upper bolts.

8. Grease shackles.

Stock configuration

Lower bolts removed

Stock vs. Terra-Flex

New shackle in place

Front - installation of new springs would be basically the same.

1. Jack up the front axle, place jack stands under the uniframe, and remove the wheels.

2. Lower the front axle and remove the bump stops. On most older XJs the bump stop cup screws out. On 97-98s the rubber bumper pulls out of the cup it sits in. Doing this means that you don't have to compress the springs as far to slide them off. If you can't get the bump stops out between coils you can leave the bump stops loose inside the spring.

3. Unbolt the bottom clamp on the springs. If you have stock length shocks you will want to unbolt them for more droop.

4. Jack one side of the axle up until the jack takes the load off the jack stand. This will compress the spring and save you work.

5. Attach spring compressor(s). Lower axle SLOWLY making sure the spring compressor stays in place. Spring compressors can be dangerous! A compressed spring designed to support the weight of a truck can release with enough force to break bones. Always compress the spring evenly, making sure it doesn't bow out to one side. If the spring compressor insist on sliding you can clamp vice-grips lightly on the springs to keep the compressor in place. If the spring bows way out to the side DO NOT keep lowering the axle. If this happens jack the axle back up, release the compressor, and start over.

6. At this point you should be able to remove the coil spring. If not just compress the spring a little more. The Terra-Flex lift replaces the factory spacer (also called an isolator), so remove it and slide the new one on. A bit of persuasion with a rubber mallet was needed to slide the space up the tower.

7. Replace the spring and jack the axle up, making sure the spring and shock seat at the top. Release the tension on the compressor, bolt the shock in, lower the axle, and replace the bottom spring clamp. Make sure the bottom of the spring is against it's seat (if it isn't you should be able to rotate it by hand). If you removed the bump stop replace it now.

8. Repeat 4-7 for the other side.

8. Replace the tires, check that the springs seated correctly, and you're ready to wheel!

Spacer in place

Conclusions

On the 91 XJ did not have any vibrations or other problems. The new Pro-Comp shocks I installed with the lift have done wonders for the ride and have much better extension than stock.

Our 97 XJ Sport with the (now removed) 1.5" lift, 225/75 tires. This is how XJs should look stock.

Stock (and slightly sagged) 91 XJ

91 XJ with 1.5" Terra-Flex lift

Twisting with the lift. The front right and back left are on the bump stops, but I ran out of room before I lifted a tire.