What goes up must come down, and the shock absorber is what keeps your vehicle from going up and down so hard you spill your coffee or lose traction on a slippery, bumpy road. The springs in the suspension actually absorb the bumps and the shock absorbers dampen the spring action so your 4Runner doesn't keep on bouncing. Without shock absorbers you could hardly climb a washboard hill without crawling up in first gear. Good shocks help the back wheels stick like glue to the road surface no matter how bumpy it gets.
Loosen the front lug nuts on both wheels with a lug wrench. Lift the front end with a jack, and lower it onto jack stands. Place wheel blocks around the rear wheels.
Loosen and remove the top bolts and nuts from the shock with a wrench. Remove the set of washers and cushions from the shock's shaft. Lay them somewhere close by in the order they were removed so you don't forget.
Loosen and remove the nut and bolt from the lower arm at the base of the shock using wrenches.
Install the new shock at the base first then the top, tightening the bolts firmly with a wrench. Make sure you keep the washers and cushions in the right order.
Lower the vehicle off of the jack stands and onto the ground. Remove the wheel blocks.
Raise the rear end of the vehicle onto jack stands, lifting it by the axle. Place wheel blocks around the front wheels.
Loosen and remove the lower shock bolts using wrenches.
Loosen and remove the upper shock bolts using wrenches.
Install the new shocks in the reverse order of removing them but do not tighten the shock bolts yet.
Lower the vehicle onto the ground then tighten the shock bolts. Bounce on the bumper a few times to help the bushings get seated properly.
