HOWTO: Rear of Trailing Link Bushing Install Tutorial

[williaty]

I finished this tutorial at about 3am local time and no one is awake to proof-read it. If you find errors, please PM them to me.

Also, I posted this hear to keep it with its companion tutorial on the trailing link swap. If a mod feels they're better placed in the DIY forum, please move them.


I'm writing this tutorial for kind of a strange reason: The install is very, very easy. Frankly, if you can rotate your tires, you can swap your rear of lateral link bushings. The problem is that no one seems to know it. The trailing link and its bushings are an often overlooked part of the suspension. This is especially criminal when you consider how amazingly easy it is to swap both the bushings and the links in comparison to how much the swap helps address one of the biggest problems with daily driving an Impreza (driveline bounce, especially a problem for the DBW cars). This tutorial covers just swapping the rear of trailing link bushings using the Big Sky Bushing Tool (talk to BigSkyWRX to get the tool) as though it were the only thing being done. There's also a companion tutorial to this one describing how to swap the trailing links themselves. If you're doing one, you probably want to combine both installs into one meta-install because they share many of the same steps. When reading these instructions, keep in mind that these steps will only teach you how to swap the bushings using the Big Sky Bushing Tool.

By the way, clicking on any of the images will get you a larger, more detailed, image.

Start the install by jacking up the car and removing the rear wheels. The front wheels can stay on. They can stay on the ground, for that matter. Once you have the wheels off, crawl under the car from the back and look towards where the wheels normally are. You should see something that looks like this:



The lump hanging off the bottom of the knuckle is the rear of trailing link bushing. The trailing link extends from that bushing on the rear forwards to where it bolts to the chassis. We'll be removing the rear bolt to swap the bushings.

OK, now that you know what you're working with, get out from under the car and look into the wheel well just in front of the brake rotor. You'll see two lines bolted to the trailing link. They'll look like this:


We need to detach both of these lines from the trailing link before removing the link. While it's not strictly necessary to do this, you'll have a REALLY bad day if you manage to cut the ABS sensor line during this process. There are two parts to the bracket. If you look at the previous picture, there's a hoop that sticks up on top of the link and a bolt farther up the link. Use a 12mm socket to remove the bolt on top of the link and then crawl back under the car to remove the bolt holding the hoop. Do this on both sides of the car. Since you can't see the second bolt from beside the car, here's a view from underneath, showing the bolt (note that your bracket might look slightly different depending on model year):


Next up is detaching the rear end of the railing link itself. Strangely, the nut is on the outside of the trailing link between the knuckle and the brake rotor. This makes it slightly tricky to find and to loosen. This picture is taken from the rear, showing you the bolt you'll be working on and how it hides behind the rotor:


The best way to remove the nut from this bolt is to use a pair of 6-point combination or box wrenches (NOTE: DO NOT TRY TO USE 12 POINT WRENCHES. If the nut is corroded in place, 12 point wrenches will very likely round off the nut) and a heavy (2.5lbs or greater) plastic dead-blow hammer. A socket and a breaker bar could be used on the head side, but would not fit on the nut side. Place one wrench on the head (inside of the bolt to prevent it from spinning. Place the other wrench on the nut (outside) in a position that allows it to be easily struck with the hammer. Strike the end of the wrench VERY HARD with the dead-blow hammer. This is not a time to be gentle and worry about breaking something. You need to be in full-on "Lothar SMASH!"-mode here. Keep beating on the wrench until you can spin the wrench by hand. After that, use a ratcheting wrench on the head side while holding the nut still to remove the nut. Now remove the bolt from the link. CAUTION: Depending on manufacturing tolerances, this bolt may be under considerable strain. It is possible that the link will spring away from the knuckle and/or that the knuckle will spring away from the link (taking the lateral links and strut with it) when you remove this bolt. Don't have you head in the way!

At this point, you get to experience the wonder that is the Big Sky Bushing Tool. This specially designed tool is a miracle of cleverness. The first thing we need to do with the tool is get it ready to use. Hopefully, the person using the tool before you would have been kind and cleaned it before returning it. However, some people suck. Make sure the tool is clean inside and out and that there's no grit or metal shavings in the threads of the rod. After cleaning the tool, lightly lube the threaded rod with silicone grease.

To get the existing bushings out of the knuckle, the tool must be configured into Removal Mode. I'm going to give both a verbal description of how to do it, and provide 3 pictures of it (an overview and 2 close-ups). You may want to print out the full-sized version of at least the Overview of both Removal and Installation so you can look at them while you're under the car.

Overview of Removal Mode:


Detail 1:


Detail 2:


First, spin one nut about 3" down the shorter piece of threaded rod. Now slide a ratcheting pass-through wrench (such as a Gear Wrench Vortex wrenches) down over the rod and onto the nut you just spun down the rod. Spin another nut about 1/2" down the rod, effectively trapping the wrench on the rod. Slip a washer down the rod to sit on the nut you just added. Add a 3rd nut to the end of the rod, sandwiching the washer between 2 nuts. TIGHTEN THE HECK OUT OF THE TWO NUTS SANDWICHING THE WASHER. Basically, you're trying to lock the two nuts against each other with the washer in the middle so neither nut can spin.

Now flip the rod over so you can add things to the other end. Place the Bearing Spacer on the rod and let it slide all the way down to the nut and wrench. Place the End Cap Bearing washer onto the rod with the smaller flat side facing the Bearing Spacer. Slide the Bearing Washer down onto the Bearing Spacer. Place the End Cap onto the rod with the flat side facing the Bearing Washer and slide it down. Finally, place the large Tapered Tube with the smaller end facing the End Cap onto the rod. The assembled Tool should look like Detail 1 at this point. You're ready to go to the car!

Crawl under the car and locate the hole through the center of the existing bushing. Slide the end of the threaded rod through the bushing so that the large, open end of the Tapered Tube comes to rest against the knuckle. Place the Plunger onto the end of the threaded rod where it comes out the other side of the bushing making sure that the indented side of the Plunger faces the bushing. Thread a nut onto the rod on the other side of the Plunger and twist it down until the rod just pokes out of the nut. The Tool should now look like Detail 3.

On the inboard side of the tool, spin the nut that's inside the ratcheting wrench down until it's finger tight against the Bearing Spacer. Place a combination or box wrench onto the very inboard-most nut so it sets up against the washer. At this point, the tool should start to stand out from the knuckle on it's own and look like this:


Get all of the parts of the Tool lined up so they stack into a nice cylinder and tighten the ratcheting wrench just enough so that the Tool doesn't try to sag out of shape. If you try to keep tightening past this point, the threaded rod will just start spinning along with the ratcheting wrench. To prevent this, hold the wrench on the end to prevent the rod from spinning. By pulling the wrench towards the knuckle very slightly you will cause it to cam against the washer, allowing you to prevent it from falling off the nut without having to pay any attention to it.

Now tighten the ratcheting wrench.

A lot.

A whole lot.

Long past the point where the small muscles in your shoulders are begging for mercy.

Tighten it until the tool falls off the knuckle.

Congratulations, you've just removed the bushing. Now hurry up and go do it on the other side.

[williaty]

Once you have both bushings out, you need to rebuild the tool in Installation Mode. As before, I'll provide 3 pictures as well as a text description. One is an overview, the other two are close-ups. I recommend you print out at least the overview for looking at while under the car.

Overview of Installation Mode:


Detail 3:


Detail 4:


Take the longer piece of threaded rod and spin a nut about 3" down the shaft. Place a ratcheting wrench down the rod and onto the nut. Spin a nut about 1/2" down the rod, trapping the wrench. Drop a washer onto the rod and chase it with another nut to sandwich it again. As before, tighten the crap out of the nut sandwich to make sure it can't move.

Flip the rod over and slide the Bearing Spacer all the way down the rod until it stops against nut/wrench. Follow the Spacer with the Push Rod. Place the Plunger onto the threaded rod with the indented side facing away from the Push Rod.

Now, put on a pair of gloves and lube up. You need to coat the bushing, the inside of the Tapered Tube, and the inside of the knuckle with silicone grease such as SilGlyde from NAPA. Too much grease won't cause a problem (other than dirty clothes) but too little grease can make the install harder than it should be.

Place the greased bushing into the wider end of the Tapered Tube so the hole in the center of the bushing is parallel to the hole in the center of the Tapered Tube. Press the bushing down into the Tapered Tube until it sticks, taking care to keep the hole in the bushing lined up with the Tapered Tube. Now take off your gloves so you don't get grease all over everything else. Slide the bushing/Tapered Tube combo onto the threaded rod with the bushing facing the Plunger. At this point, the Tool should look like Detail 3.

Get under the car with the Tool and slide the threaded rod though the hole in the knuckle. On the other side, put the End Cap onto the threaded rod with the flat side facing away from the knuckle. Add a nut to the end of the threaded rod and spin it down until the rod just pokes through.

Move to the inboard side of the tool and spin the nut in the ratcheting wrench down with your fingers until it tightens up against the Bearing Spacer. At this point, you'll probably want to have a friend help you as 4 hands work better than 2. The End Cap needs to be seated properly against the knuckle. If you slide it around a bit, you'll feel one point where it just kind of locks into a perfect fit against the knuckle. It won't want to stay here without a little help though. The Tapered Tube on the other side of the knuckle is the same way. You'll be able to run a finger around the place where the Tapered Tube hits the knuckle and feel if the Tapered Tube is centered on the knuckle. Center it and then hold it there.

The rest of the Tool should just fall into place as you slowly tighten the nut. Tighten the nut with your fingers or the ratcheting wrench until the Tool will hold its own weight without slipping out of alignment. It should look like this at this point:


Verify one more time that the End Cap is properly seated against the knuckle and that the Tapered Tube is properly centered against the knuckle. The alignment of these two pieces of the Tool is the only thing that makes sure the bushing goes in right. Screw up the alignment, and you're going to screw up the install.

Now tighten the ratcheting wrench.

A lot.

More than twice as much as you did last time.

Your little muscles in your shoulders are going to think back fondly of the halcyon days when they only had to remove bushings.

Eventually, the ratcheting wrench will come to a sudden stop as though there had been metal-on-metal contact (note that the Tapered Tube may fall off or become crooked just before this point, it's nothing to worry about). Guess what? There was metal-on-metal contact. You've just driven the bushing clear though the knuckle until the metal sleeve inside the bushing crashed into the End Cap. You had to do this so the dust boot on the bushing would pop free of the knuckle and take it's proper place.

Loosen the ratcheting wrench until you can remove the nut holding the End Cap onto the threaded rod. Remove the tool from the bushing.

The bushing is obviously not centered in the knuckle, which is bad. However, we had to push it that far out to get the dust boot to pop. Now we have to pull it back to center.

Take the Tapered Tube and the Push Rod off the Tool and set them aside. You need to switch the tool back to Removal Mode except for using the longer rod. Place the End Cap Bearing Washer onto the rod followed by the End Cap. Place the Tapered Tube onto the rod with the large end facing the knuckle.

Place the threaded rod through the bushing. Place the Plunger on the threaded rod with the indented side facing the bushing. Thread a nut onto the rod, trapping the Plunger against the bushing. Line up the Tool properly and tighten it until it will hold its own weight.

At this point, have a friend place their fingers against the outboard side (closest to the rotor) of the bushing. While you tighten the bushing, they will feel the bushing move. At first, the bushing will be convex (domed up towards them). As you pull the bushing into the knuckle, it will become flat, and then concave (dished into the knuckle). They need to tell you to stop the moment they feel the bushing go from flat to concave.

Once they tell you to stop, loosen the ratcheting wrench and remove the tool from the bushing. Now you need to feel the bushing to decide if it's properly centered. Reach under the knuckle with one hand. Pinch the bushing's steel core between your thumb and forefinger as though the bushing were dirty and you didn't want to touch it. If you can't picture that in your head, here's someone holding a different bushing from a different install in the grip I'm talking about:


Keeping your hand in this shape, run your fingers around the rubber of the bushing, right next to the steel core. You should be able to compare the inside and the outside of the bushing. Ideally, both sides will feel the same (very close to flat, a TINY bit concave). If one side feels more or less concave or convex than the other, the bushing isn't centered and needs to be moved slightly using the Tool. The Tool in Removal Mode will move the bushing towards the center of the car. The Tool in Installation Mode will move the bushing towards the outside of the car.

Keep using the Tool to slide the bushing back and forth until you get the bushing centered. It's a pain in the butt, but you need to get it centered.

Now go do it to the other side!

Once you have both bushings installed and centered, it's time to put the car back together.

Move to the rear of the trailing link and slide the link up and around the knuckle. It's very likely that the hole in the link and the hole in the bushing will not be aligned. You will need a friend to push or pull on the knuckle until the holes are aligned and the bolt can be slid home. On some cars, this will require a VERY large amount of force, so be sure you have the wheels securely chocked before you try to move the knuckle into alignment. Place the nut onto the bolt and again tighten it finger tight but no more.

Rubber has a property called hysteresis. For our purposes, this means that whatever position we tighten the bolts down in is the position the rubber bushings are always going to fight to return to. For a car, this obviously means we need to tighten them down at ride height. The best way to achieve this is to use a floor jack. Place a piece of 4x4 on the jack and raise it up under the knuckle. Make sure the wood and jack are positioned so that you can swing the wrench when you tighten the bolt (note that the picture below shows the jack in the wrong position for this install, you actually need to bring the jack in from the rear of the car). Raise the knuckle with the jack until the knuckle is at ride height or the chassis begins to lift off the jack stands. Note that the chassis must still have its weight resting on the jack stands for safety. The picture below shows the basic idea, but remember that the jack is in the wrong position in this picture, you'll need to bring the jack in from the rear:


Use a torque wrench and 17mm Crow's Foot to torque the rear bolt to 66lb-ft. Use the same setup to torque front bolt to 85lb-ft. Drop the jack slowly to let the knuckle down. Do this on both sides of the car.

Re-install the brackets holding the parking brake and other lines to the trailing links using the two small bolts. Torque these bolts to 22lb-ft.

Visually verify that everything looks correct and make sure you don't have any extra parts. Re-install the wheels using a star-shaped tightening pattern and torquing the lug nuts to 70lb-ft. Drop the car to the ground and take it for a test drive.

Enjoy!