Here’s a new shock assembly below the old one it will replace. Had we opted to simply swap out the blown shock, we’d have to take apart the original assembly, and re-use its old top mounts, coil spring, bushing, and boot with the new shock. (Image/OnAllCylinders – Paul Sakalas)

Make no mistake, shocks and struts are regular wear items. That’s because, as your car or truck racks up miles, your struts and shocks will fatigue and lose the ability to control the spring’s compression and rebound—which will adversely affect your vehicle’s handling characteristics and ride quality.

Problem is, unlike a dead battery or blown tire, a shock’s gradual wear typically occurs over years and the performance decline can be subtle. For that reason, it’s not uncommon for shock wear to go unnoticed in a daily-driven vehicle.

So, then…

How Can You Tell if Your Shocks are Blown?

While it’s impossible to diagnose every vehicle with a blanket set of symptoms, there are some common issues that usually point towards worn-out shocks or struts.

  • Shimmy/shaking while vehicle crosses bumpy or uneven road surfaces
  • Loud clunks (from spring rebound) when crossing low speed bumps
  • Bouncy, floating feel when vehicle is moving at highway speeds
  • Excessive body roll/lean when cornering
  • Nose diving during hard braking
  • Body sag, lowered ride height

We dove into this subject in more detail during one of our Mailbag features and you can read it here: Diagnosing Worn Shocks & Struts

Don’t get caught up in the shock or strut nomenclature here: they both basically do the same job, and for the purposes of this article, there’s no real distinction—but you can watch this video here to learn the difference between shocks and struts.

This crusty-looking rear shock is on a 2012 Subaru Outback. The vehicle developed a noticeable rear shimmy while crossing bumps at highway speeds, a sure sign of a blown rear shock. With 175K+ miles on both rears, we didn’t bother troubleshooting left or right, opting instead to replace them both as a pair. (Image/OnAllCylinders – Paul Sakalas)

Understanding Shock Assemblies & Loaded Shocks

Not too long ago, a strut or shock absorber was a separate component, divorced from either the coil or leaf spring. But on lots of modern vehicles nowadays, you’ll likely find your strut or shock combined with a coil spring, creating a complete assembly.

That means, in order to replace just the strut or shock, you’ll need to remove the shock/strut assembly, take apart the entire thing, replace the strut, put it all back together, then reinstall the assembly in the vehicle. While that’s not a big deal for pro shops and experienced mechanics, it can be a cumbersome job for the home DIY’er.

On the left is the Subaru’s old driver side shock, on the right is its disassembled passenger side shock. We took it apart so you can see the distinct components: the shock, coil spring, top mount, shaft bushing, and protective boot. (Image/OnAllCylinders – Paul Sakalas)

More importantly, taking apart a shock assembly ABSOLUTELY, POSITIVELY requires a specialized suspension coil spring compressor tool to do the job safely and correctly. (We’ll toss in some pictures of this later in the article.)

But, there is an alternative.

Depending on your vehicle, you may have the option of replacing the entire assembly altogether. That makes the install a far more straightforward pop-in/pop-out procedure. Along with the strut/shock, these assemblies include the coil spring and shock mounts—all bolted together and ready to go.

These individual assemblies are often simply referred to as “loaded” or “complete” struts or shocks.

Here’s a loaded strut assembly from KYB, but many other manufacturers make them as well. You’ll see the boot, coil spring, and upper mount are already in place, and it’s ready to pop into a vehicle. (Image/Summit Racing)

While they’re a bit more expensive, a loaded shock or strut can save you a ton of hassle—especially if you’ve never disassembled a strut before. As alluded to above, removing a coil spring demands a specialized tool. Without it, you risk serious injury or damage caused by unleashing the pent-up energy inside the compressed spring.

The benefits of a loaded shock or strut involve more than convenience too. If you’ve got a really old shock or strut assembly, like our 175K-mile Subaru specimens here, there’s a good chance the upper mounts are worn out as well.

And that’s important because, on a lot of cars and trucks, the upper mounts are clad in rubber to help reduce road noise and vibration. Replacing the top mounts during a shock install can help restore some of those qualities.

Better still, you’ll likely get shiny new hardware too.

So even though we safely took apart the shock assembly for this article, we still opted to go with a loaded shock with all-new components (instead of simply replacing the individual shock) for all of those reasons outlined above.

Replacing Shocks & Struts

With the tricky shock disassembly out of the equation, popping in a new set of rear shocks on our 2012 Subaru Outback was pretty dang easy. (Hat tip to YouTube’s SubieTech 1.6L for the quick walkthrough video.) You simply jack the car up, remove the wheel, remove a handful of bolts for the sway bar, shock eyelet, and body mount, and take off the pair of top-mount nuts from inside the rear trunk floor. From there, you just swap the assemblies for the new ones.

With the new loaded shock assemblies in place, the job was pretty much done, save for some bolt tightening and cleanup.

Here’s the new shock assembly in its rightful place. Note the floor jack—we used it to position the bottom suspension arm/bracket so all of its bolt holes (sway bar, body mount, etc.) lined up correctly. (Image/OnAllCylinders – Paul Sakalas)

Awww Heck, Let’s Take Them Apart Anyway!

Since we had a set of spring compressors handy, we went one step further and took apart the shock to show you the shock disassembly process in a bit more detail.

Disassembling a strut or shock isn’t necessarily a tough job, but again, it demands the right tools and there’s little margin for error. That’s because, even off the vehicle, the coil spring is still significantly compressed inside the shock assembly.

So if you try to take off the top mount without using proper spring compressor tools, there’s a good chance that the mount and spring will fly off with significant energy—we’re talking penetrate-sheetmetal or shatter-jawbone type force here, so be careful!

Check out the pics below and you’ll get a good idea how these particular spring compressors work.

While spring compressor tools come in a few different forms, we used this set designed for MacPherson struts. The brackets mount to either side of the spring and lock into place with the safety retaining pins. Then you turn the nut at the top (preferably using an impact or power wrench) to compress the spring for disassembly. (Image/OnAllCylinders – Paul Sakalas)
OK, so here are the spring compressors in place. By tightening the nuts, you slightly compress each side of the spring. Don’t go crazy, just compress the spring enough to take all of the pressure off the top mount. Note that the locking pins are in place to prevent the brackets from slipping off the spring. (Image/OnAllCylinders – Paul Sakalas)
Once you have the spring compressed enough to take pressure off the top mount, you’re ready for disassembly. In most cases, you’ll find that a single nut threaded onto the shock piston holds the entire thing together. A quick whack with a 14mm impact socket was all it took to remove the lone center nut. (The other two nuts, top and bottom, are to mount the shock to the vehicle.) Once the top mount is removed, you simply loosen the bolts on the compressor tools to slowly decompress the spring until it’s fully extended. (Image/OnAllCylinders – Paul Sakalas)
Here’s another pic of the disassembled shock, alongside the spring compressor tools. Check out how long the uncompressed spring is to the right. It extends well past the top of the shock’s piston rod—that should give you a good idea of how much energy is stored in the compressed spring when it’s assembled. (Image/OnAllCylinders – Paul Sakalas)

Author: Paul Sakalas

Paul is the editor of OnAllCylinders. When he's not writing, you'll probably find him fixing oil leaks in a Jeep CJ-5 or watching a 1972 Corvette overheat. Thanks to a penchant for vintage Honda motorcycles, he spends the rest of his time fiddling with carburetors and cleaning chain lube off his left pant leg.