Mario's Rear Shock and Spring Replacement Procedure v.2.0
This procedure is meant to be a reference on the removal and replacement of the rear shocks, springs and shock mounts. If you read past this paragraph and you decide to apply anything that is contained within this reference you are assuming total responsibility and liability for your actions including but not limited to damage to your or someone else's vehicle or person. I know my mechanical abilities, but it's more important that you know yours, because I cant. If you feel that this is over your head, don't do it and get a professional to do it.
This procedure can be used to replace the rear shock mounts, springs and shocks with either OEM replacement or high performance aftermarket parts all at once or on an as need basis. It's a lot easier and most time effective if it is all done in one shot.
If you follow the procedure as described in the Bentley manual it WILL take you in excess of three hours as they instruct you to remove the rear drive axles and believe me it IS NOT FUN.
I have done this procedure a total of three times (once on a '98 M3 and twice on my '97 Z3, 1.9) and now have it down to less than 30 minutes per side. I have inspected the shock mounts on the Z3 at least twice. I would recommend that the Bentley manual be used as a reference for images and torque values.
One thing that I did not include is a comprehensive listing of the appropriate metric socket sizes. I will include that information in v. 3.0 I would appreciate it if and when someone follows the procedure that they write down what size sockets they used and where and let me know. If there are other suggestions or insights, let me know and they will be included in v. 3.0
Quick reference: Shock & Shock Mount inspection, removal and replacement
Follow steps 1 - 14 and pick up again on step 19
Spring inspection, removal and replacement
Follow steps 1 - 28
The Procedure - Lets have some fun:
1)Get under the car while it is still on the ground or on car ramps (much, much easier) and disconnect the rear anti-roll bar. It is a lot easier to disconnect it when it is an almost neutral state (weighed down) of load. If you do not, the weight of the drooping rear trailing arm will literally bind the anti-roll bar end links and bushings and make it impossible to remove. In addition, if you leave the anti roll bar attached, you will not be able to gain sufficient rear trailing arm drop to pull the spring out later! If the car was on car ramps, drive it off.
2)With the top up, gain access to the top boot. There are two ways you can get access to the rear - 1. Straddle the center console - gotta have long thighs for this one, if you do not, place some towels on the seat to extra height and also place a towel on the rear storage bin console for padding comfort. This method gives you equal two arm access to either side of the rear. This method is good if you have HMS or BMW roll bar and roll hoops respectively. 2. Sitting on your knees on the seat bottom facing backwards. If you will be working on the rear left side of the car, sit in the right seat, if you will be working on the rear right side of the car sit in the left seat. It helps to move the seat forward a bit and then recline the seatback as much as possible. This was my preferred method, before I installed a HMS sportbar (the one with the diagnoal tube) on my then roll bar less '97.
3)Remove clips by using a medium sized nail remover/pry bar (Stanley makes one that is 10" long and works well)
4)Pull carpet down and away from each rear corner (no need to remove all of it) to gain access to the rear shock mounts. If it proves difficult to remove by hand, stick a screwdriver into the carpet mounting hole left open by the now removed carpet clip and pull down.
5) Remove Dust Cover - stretch it to one side and then up and over
6) Loosen wheel lug nuts
7) Jack up one side of the car or jack stand the entire rear
8) Remove wheel
9) Place hydraulic jack under the rear trailing arm, right below and behind the wheel hub and brake caliper. Pump jack to the point where the pressure of the jack lifts the trailing arm a bit.
10) Loosen the shock absorber to trailing arm bolt, but do not remove
11) Climb inside the car and loosen and remove the rear shock mount nuts. Also remove the shock nut and associated washer. When removing this nut, you will need two wrenches - one to hold the shock shaft (small adjustable wrench) and an open end wrench to loosen and remove the nut. If you just try to remove the nut, it will turn and turn. The washer is bigger than the hole it has to go through. If left on, you will not be able to remove the shock! The pressure of the jack under the trailing arm should keep it in place while you remove the hardware.
12) Go to the jack and lower the trailing arm slowly while holding on to the shock tube to prevent the shock from falling forwards or backwards.
13) While holding the shock, proceed to remove the shock to trailing arm bolt
14) Remove shock and shock mount assembly as they will come out in one piece (if you are replacing shocks and shock mounts see "A" below)
15) This will now give you clear and easy access to the rear spring. Lower the jack slowly and watch the spring as it slowly releases its tension as the trailing arm drops.
16) Lower the trailing arm enough (you may have to push it down further by hand) so that you get a large enough gap between the spring seat and the spring to be able to pull out the spring by hand. If it proves too hard to remove, use a pry-bar stuck into the top coils of the spring to work the top of the spring loose enough to pull out.
17) Pull out the old spring and insert the new. Chances are that the new spring will be a cinch to insert as it is overall height will be lower than the OEM spring you just pulled out.
18) Pump jack to compress and seat spring. After seating the spring, lower the jack and control arm enough to make sure that when you mount the bottom of the shock to the trailing arm, there is enough clearance to get the top of the shock shaft under the shock mount hole.
19) Take shock assembly and attach lower shock tube to the trailing arm with the shock to trailing arm bolt. Tighten but not to spec. torque.
20) Hold shock while pumping jack and just before the shock mount is to go through the shock mount hole in the wheel well, re-align the shock mount studs with the shock mount holes. Then keep pumping until the top of the shock and mount are all the way through.
21) Go inside the car and re-fasten the shock mount to the chassis and shock shaft nut and washer to spec torque.
22) Return to lower shock mount and tighten to spec torque.
23) Lower jack and remove
24) Since the rear suspension is at full droop, it really gives good access to the anti-roll bar end links, so take the opportunity to lubricate them now.
25) If the car is on jack stands, repeat procedure for the other side. If not, go to step 26 and then back to step 6 or 7.
26) When complete, re-attach wheels and lower car
27) Re-attach anti-roll bar.
28) After the other side is complete, go back inside the car, mount the upper shock dust boot, push the carpet in the roof boot back into the corners making sure that the carpet edges go below the metal trim/roof anchor piece, adjust carpet if necessary and re-insert the carpet fastners in the appropriate holes. "A" - Rear shock / shock mount inspection / removal or replacement
At this time you will have both the shock and shock mount out of the car. It is a good time to inspect the shock and shock mount or replace one or both with something else. You already removed the nut and washer that hold the shock mount to the shock itself, so to remove it is just a matter of pulling it off. To place the shock mount back on the shock shaft is just a matter of pushing it back on. At this time you may or may not want to remove and replace the shock mount to chassis paper gasket with a new one. If necessary also replace the shock with a new one at this point.
Whenever you are done with your inspection of both the shock mount and shock, slide the shock mount back onto the shock shaft and put it aside until step 19.
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