Change your shock absorbers

Latest revision as of 16:34, 3 March 2010

I have just done this on the Valiant, sorry no pics, but it will depend on your car what it looks like anyway.

[edit] Overview

Dampers (commonly called shock absorbers) are usually oil filled cylinders which retard the movement of the springs by forcing the oil through one or more valves. This "damps" the simple harmonic oscillation of the springs and keeps the tyre on the road for as much of the time as possible. For more info on how dampers work, reply to this thread and I will write an explanation. Gas shocks are regular oil filled shocks which have been pressurised with inert gas to reduce foaming etc of the oil and ensure a more consistent operation. "Air shocks" use compressed air instead of oil, actually do some springing and can change the ride height/damping by changing the pressure. After a lot of use the valves become worn and let more oil through, reducing the damping effect. The dampers then need to be replaced (usual) or rebuilt (some McPherson struts and expensive dampers ie the Bilsteins on my rally car).

[edit] Disclaimer

Neither the entity known as "badger" nor Agg nor OCAU shall be under any liability for your death, or any bodily injury, loss or damage which may be sustained or incurred by you as a result of reading, relying upon or following this "motoring guide" except in regard to any rights you may have arising from the Trade Practices Act, 1974.

Because this is a general guide, and all cars are different, your car may differ to the car described below. It's not that hard. Have a look, you should be able to figure it out by yourself. If not, ask someone or get a workshop manual.

[edit] Warnings

Remember: be smart, look at it and think about how it can hurt you before you play with it. If you don't know or are not sure, ask: "there are no stupid questions, just stupid people".

The main dangers here are having the car fall on you and releasing a compressed spring so it hits you with great force. With due care you can easily prevent either of these happening. Smaller things, like ripping skin off your knuckles after the spanner slips of the bolt are all part of the fun of being your own mechanic. Just think of the money you are saving and wash it clean afterwards.

[edit] Tools

• Wheelbrace
• Jack (I got a trolley jack for $50)
• Axle stands (I got these for about $40 (set of 2), rated to 2000kg each)
• Spanners
• Socket set with long handled ratchet/bar
• Hammer (+ small block of wood)
• Long big screwdriver (for levering)
• Punch or small screw driver for knocking bolts out
• Ball joint removing tool

[edit] Parts

• New dampers (shock absorbers)

I prefer to call them dampers, as the springs actually absorb the shock, the dampers control the springs. I used Gabriel heavy duty on the rear and monroe GT Gas on the front (got these for free, otherwise I would have got gabriels for the front too). Note that the Valiant is used almost exclusively for towing. I DO NOT recommend heavy duty/highly damped/very hard dampers for regular road cars unless they will be carrying heavy loads. They WILL NOT improve handling (the same as stiffer springs will not necessarily do so). I do recommend buying good quality dampers.

• New split pins, if you have to remove any.

[edit] How to do the job

This depends on the type of suspension you have.

[edit] Rear

Live axle, beam axle, swing axle or some type of IRS. These are pretty much the same, whether leaf springs or coil springs. as long as you don't have struts (ie the damper is in the middle of the spring) you are ok:

1. Loosen wheel nuts with wheel brace.
2. Jack up the rear wheels, put the axle stands under the chassis rail just in front of the front of the wheel. check that it is stable (do all this on a hard flat surface).
3. Remove the wheels and place under the car near the axle stands (this is so if the car falls off the stands (which it shouldn't) the wheels will stop it from falling onto the ground and completely crushing you).
4. Look under the car at the dampers. they should be fully extended, attached at the top somewhere near the front of the boot, and at the bottom near the hub (where the wheel joins the axle). Some dampers are attached from the top (in the boot), others slide onto a bolt nearby.
5. Getting your socket set, undo the nut holding the damper on at the bottom.
6. Undo the bolt holding it on at the top (you may want to do 5 and 6 in the other orderdepending on whether the damper will fall down when you undo the top (in the boot)
7. Pull the old damper off the bolts, use the screwdriver for leverage if need be. Note the direction in which it is fitted. It will usually have the outer part (which covers the other part when the damper is compressed) at the top
8. Put the new damper on. You may need to compress it slightly to get it on. Don’t worry if you can’t get it completely on, the nut will pull it into place as you tighten it.
9. Put the nut on, tighten it up. As tight as you can get it with a normal socket is usually ok, there is not a lot of stress on these nuts. For boot mounted dampers, you might need a certain torque, check you workshop manual, but the previous is usually ok.
10. Repeat steps 4-9 for the other side
11. Replace wheels, do up wheel nuts
12. Jack up car, remove stands, lower car, tighten wheel nuts again.
13. Lean on boot to make sure suspension travels ok.

[edit] Front

For wishbone and torsion bar type suspension (where the damper is not inside the spring), read on. For McPherson struts (much harder) see note at end:

1. Loosen wheel nuts with wheel brace.
2. Jack up the front wheels, put the axle stands under the chassis rail just behind the rear of the wheel. check that it is stable (do all this on a hard flat surface).
3. Remove the wheels and place under the car near the axle stands (see note for rear 3.)
4. as before, look at your dampers. They will usually be attached at the top with a nut, accessible from the engine bay, the bottom will usually be attached to the track control arm with a bolt passing through it.
5. Using socket set again undo the nut at the top.
6. Undo the nut at the bottom. You will usually need to put a spanner on the head of the bolt and undo the nut with the socket.
7. Try to pull the bolt out. When it won’t come out, put the nut back on the bolt for about 3 turns (this protects the thread). Using the block of wood to further protect it, hit the nut with the hammer to knock it through.
8. When the nut is touching the TCA, take it off the bolt. Use the punch or screwdriver to push the bolt out of the TCA.
9. Remove the damper. You may need to compress it to get it off .
10. put on the new damper (you probably need to compress it to get it on {note: they usually come with some wire holding it partially compressed, only remove this once 11. is done}).
11. Have a lot of trouble getting the bolt back through the TCA and damper. Usually compressing it helps. Put nut on and tighten
12. Let the damper extend up (ie cut wire if applicable) and do up nut on top. You may need to put a jack under the hub to push the damper up into the correct spot.
13. Repeat steps 4-12 for the other side
14. Replace wheels + nuts, jack up remove axle stands, lower, retighten wheelnuts.
15. Lean on bonnet to check operation.
16. Put tools away.
17. Get yourself a beer, you are done.

Note: McPherson struts: In this type of suspension, the damper is incorporated into the struts, and the spring is around it, highly compressed. Removing the damper section (insert) is quite dangerous as the spring pressure must be released (using spring compressors) and then the insert removed. Often (if you have the original strut) the damper can be rebuilt as a much lower cost.

My advice would be to remove the whole strut, and take it to your friendly suspension shop, and get them to rebuild/replace the insert. Most will do it for a minimal (or no) fee if you are buying the dampers from them (esp if you get the rears from them too).

Removing the strut:

1. Steps 1-3 above
2. Undo the nut on the ball joint on the bottom of the strut. If castle nuts are used, first straighten split pins using pliers, then pull the pin out, then undo nut. Using ball joint separating tool, separate ball joint from strut. TCA should now be separated from strut.
3. Same thing with tie rods (steering)
4. Same for anything else attaching the bottom of the strut to the rest of the car
5. Undo three (usually) nuts attaching strut to strut tower (engine bay). NOTE: Don’t undo the centre bolt, as the spring will shoot the end of the strut off, possibly decapitating you!
6. Repeat steps 2, 3, 4 and 5 for other side
7. Take struts to shop
8. Replace by doing all the nuts up again. Remember to replace split pins if any part uses castle nuts (usually ball joint, tie rods)
9. Steps 14, 15, 16 and 17 above

[edit] More Info

KYB shocks and struts installation on TJ Magna wagon

[edit] More Links

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