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How to replace individual shock absorbers

The shock absorbers on your vehicle dampen (or restrain) the vibrations that the suspension springs can create as your vehicle travels over various road surfaces. Put simply, shock absorbers keep the tires on the road by keeping the springs from bouncing up and down continuously.

After countless up and down cycles of vehicle dampening, the shock valve and piston become worn, gradually losing their effectiveness. If your vehicle has over 75,000 miles, or its ride and handling aren't as smooth as they used to be, it may be time to replace your vehicle's shock absorbers.

Types of shock absorbers
For vehicles produced in the last few decades, shock absorbers can be classified into two basic types – individual or stand-alone shocks that attach to the vehicle suspension and frame, and shock-absorber units (or cartridges) integrated into a suspension strut – technically, a MacPherson or Chapman strut. Bear in mind that some cars have struts in the front and individual shocks in the rear. If this is the case, you can replace the rear shocks, but the front struts are better left to a professional.

The integrated shock absorber/struts can be quite difficult to replace. Many times they require removal of the suspension springs and the strut unit, which is beyond the scope of this DIY project. Although many newer vehicles use struts, most older vehicles, and most new or old trucks and SUVs, have individual shock absorbers in both the front and rear. This DIY car maintenance article will describe how to replace those individual shock absorbers.

Park your vehicle inside or outside in a well-lighted level area. Unless you have a pickup truck or sport utility with lots of ground clearance, you must remove the wheels to determine whether your vehicle uses struts or individual shock absorbers, or whether the front and rear have different systems. You will only need to remove one front and one rear wheel (one at a time) to see this. Use all appropriate safety precautions.

Once a wheel is removed, you should be able to determine what type of system you have. If your vehicle is equipped with struts, it should look like this:

  • The strut is a tube that is 2 or 3 inches in diameter and 20 to 30 inches long. It is mounted vertically behind the wheel hub and brake.
  • The vehicle spring surrounds the strut, usually on the upper half.
  • For the front suspension, the strut tube rotates as the steering wheel is turned.

If your vehicle is equipped with individual shock absorbers, it should look like this:

  • The shock absorber is tubular like a strut, but shorter, usually only 12 to 18 inches long.
  • The ends of a shock absorber have either a ring welded to them for a bolt to pass through or an exposed rod that is threaded. This threaded end goes through a hole in the vehicle suspension member or frame.
  • For the rear suspension, the shock absorber will have a similar attachment, but it will often be located between the vehicle frame and the rear axle.

If you are having trouble telling a strut from a shock absorber, visit your local automotive parts supply store or car dealer parts counter and ask to see the shock/strut for your vehicle, or a picture of it. Make a mental note of the shape and location, look for that specific shape on your vehicle, and see how it is attached.

Once you have identified that your vehicle does have shock absorbers rather than struts, you need to determine your ability to handle the job of replacing them.

Take a close look at the ends of the shock absorber and their attachment hardware:

  • Can you see the bolts and nuts that hold it in place?
  • Is the top mounting under the hood or inside the trunk?

Take a close look at all the fasteners. Since it can take many years to accumulate 75,000 miles, the fastening hardware may be quite rusted. Check to see if you have the right wrenches to fit the bolts and nuts. If possible, check to ensure that you can loosen the fasteners.

Point of no return
The point of no return is determined by your ability to remove the fasteners that hold the old shock absorber units.

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Tools required
Basic hand tools are needed for this job:

  • Socket wrenches (metric or SAE, depending upon your vehicle)
  • Combination wrenches (metric or SAE, depending upon your vehicle)
  • Large, flat-bladed screwdriver
  • Vise grips (optional, depending upon the type of shock absorber)
  • Rust penetrant
  • Vehicle jack and jack stands

You can obtain good replacement shock absorbers from your local parts store or your vehicle's dealership. Check the hardware that is included with the shock, since you may need to buy an additional hardware kit to replace the original rusted or broken fasteners.

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The job
Locate your vehicle in a well-lighted level area, either inside or outside. Give yourself plenty of access around each wheel.

Step 1: Jack up the car until one wheel is clear of the ground and support the vehicle with a jack stand. Follow all appropriate safety precautions. Remove the wheel/tire.

Step 2: Once the wheel is removed, locate the lower attachment bolts and nuts of the shock absorber and remove them. If necessary, use the rust penetrant.

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Step 3: If the suspension arms drop when the lower bolt is removed, or if you can't push the bolt out once the nut is removed, you may have to use the jack to take the load off of the lower suspension arm. To do this, you will need to locate your jack under the lower point where the shock absorber attaches to the suspension arm (or the axle). Make sure that the jack is lifting on a solid point on the lower suspension arm or axle. Raise the jack just enough to take the load off the shock or to the point where the shock absorber bolt can be removed.

Step 4: Now tackle the upper attachment point of the shock absorber. If the upper attachment is the threaded end of the shock absorber piston rod, you will most likely notice that this rod rotates as you try to loosen the nut. The trick here is to hold the rod and keep it from rotating while you loosen the nut. There are special sockets available that fit over the oval end of the piston rod, but a pair of vise grips will work just as well. Remember: You're removing these old shock absorbers, so any damage to the piston rod is unimportant.

Step 5: Once the shock is free at both ends, pull it clear of the vehicle. Sometimes you will have to pull it through a suspension arm to get it free.

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Step 6: Now compare the old shock with the new one, including the hardware. You might notice that the new shock has a plastic strap holding each end together. Don't be concerned. This is used to keep the shock from expanding inside its shipping box.

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Step 7: You are now ready to install the new shock absorber, but first you need to install any washers and rubber cushions that go on the threaded rod. After installing any washers or grommets, remove any plastic strap that is holding the new shock absorber from expanding.

Step 8: Start by reinstalling the shock, attaching the top first. Attach the hardware loosely at first, until you get both ends of the shock absorber in place.

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Step 9: Now attach the bottom of the shock absorber. You will most likely have to compress the shock to align the bottom of it with the mounting holes. Gradual pressure will compress the shock; it just takes some time. Note: There is no hard-and-fast rule about top first and bottom second. Experiment to see what works best on your vehicle.

Step 10: Once the shock absorber is securely in place, you can tighten the fasteners. When you are tightening the threaded nut down onto the rubber cushions, squeeze the rubber about a quarter of an inch and then stop. Another way to determine how far you should tighten is to apply the same amount of torque (pressure) to the fasteners as was required to remove the old ones.

Step 11: Once the lower hardware has been tightened, you are finished with the first shock absorber. Remount the wheel and lower the vehicle back down. The rest of the shock absorbers should be replaced following the same procedure.

Step 12: When you have installed all the new shock absorbers and secured the wheels and tires, look around your vehicle to ensure that you have not left any debris or tools where they may get run over. Now take the vehicle for a short and slow test drive, listening for any squeaks or bumps that may indicate loose hardware.

Clean and return your tools to their appropriate place in your shop or tool kit. Properly dispose of the used shock absorbers. And that's it. You should be in for smooth sailing down the road.

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