A shock absorber on a vehicle absorbs the motion of the vehicle when you hit a bump. The "shock" of hitting the bump travels up through the wheels and into the shock absorber. By shortening and lengthening itself, the shock restrains the excessive movement so that you and your passengers are not shaken around. Toyota recommends changing your shock absorbers on the 4Runner every three to five years.
Loosen the lug nuts on the front tires. If you attempt to loosen them with the vehicle suspended in the air, the wheel will just spin. Once the lug nuts are loose, jack up the vehicle and set it on safety stands. If you have a hydraulic lift available, this is another good option.
Remove the lug nuts and wheels and set them aside. Remove the double nuts at the top of the shock absorber. It will resemble a large spring wrapped around an aluminum tube and will be attached to the axle behind the wheel. Remove the cushions and cushion retainers.
Remove the two bolts on the lower end of the shocks. If you are working on a two-wheel drive, it will be only the two bolts you have to remove; if you are working on a four-wheel drive, you will have to remove the lower through bolt in addition to the two bolts that secure the shock to the lower control arm. Remove the shocks on each side. Take note of how the rubber washers and bushings are installed and inspect them for cracks, or worn areas. Replace these parts if necessary. If you cannot remove the bolts, make sure you have replacement bolts and use a tool cutter (Dremel or similar) and cut the head off the bolt and use a new one to replace it. Use a hammer and a small flat-head screwdriver to knock the cut bolt out.
Install the new shocks and tighten the lower mounting nuts and bolt. Then tighten the upper mounting nuts and bolts. The bolts should be tightened to the factory specifications using a torque wrench. Upper bolts should be at 18 foot-pounds if it's a two-wheel drive and 47 foot-pounds if it's a four-wheel drive 4Runner. Lower bolts should be at 13 foot-pounds. The spring on the new shocks will start from the top and will not reach all the way to the bottom of the "aluminum tube." This is normal; don't worry about it.
Reattach the wheels, tires and lug nuts on the front tires. Repeat this process on the rear shocks. If your vehicle is on a hydraulic lift, you can start on the rear wheels before or after you've replaced the front ones.
