Do it yourself, change the rear shock absorbers on your Chevrolet Trailblazer. Servicing this parts is actually a quite simple task, that can be done in the back of your garage in less than half and hour. You will need an 18 mm socket wrench, with a ratchet and probably a jack stand or elevator to support the vehicle, but this is not totally necessary.
So, the easiest way to do it, is to lift the car on a jack and remove the wheel in front of the shock absorber you need to replace. But as we said before, this is not totally necessary. You can still remove the absorber with the wheel on and the car on the ground. You will just have to remove the bolts holding the absorber and you can start with the one on the lower side, as you can see in the image below.
You can do it using an 18 mm socket wrench and you might need another wrench for the opposite side, to hold steady the tip of the bolt. After you do it, you can point your attention towards the upper side of the absorber and remove the bolt there, too (see picture below).
After doing these steps, you should be able to remove the old shock absorber and this is the moment to install a new one. Secure its upper side first, with the 18 mm bolt and then the lower side and you should be ready to go. This is all you need to do, if you wish to replace the rear shock absorbers on your Chevy Trailblazer.