Floaty rear end over bumps, a clunk from the back on rough roads, or the rear of the car still bouncing after you've already passed the dip. That's your rear shocks and their upper mounts giving up. On the E36 the rubber shock mounts at the top of the tower deteriorate and start knocking, and the shocks themselves wear out around the same mileage.
This is a straightforward job with one safety catch you have to respect. Read the warning in Step 2 before you touch anything.
Before You Start
The factory calls this the rear shock absorber and its upper mount. The upper mount uses M8 self-locking nuts into the body, and there's a lower bolt that ties the shock to the trailing arm. The key detail the Bentley manual flags: the shock is what stops the rear axle and trailing arm from drooping too far, so the trailing arm has to be supported before the shock comes off, or you can damage the CV joints.
Do one side at a time so the other side keeps the suspension located. Buy new upper mounting nuts and a new upper mounting gasket, because the manual specifies fresh self-locking nuts on reassembly.
The E36's Weak Spot: A Torn Shock Tower
Before you trust a fresh mount, look hard at what it bolts to. This is the single most important thing to check on this job, and the reason a lot of E36s come back knocking. The rear shock tower is thin sheet metal, and every bump feeds the shock's load into a small patch of it around the two mounting studs. Over the years that metal fatigues, cracks out from the stud holes, and can tear the mount right up out of the tower and into the wheel well. A dead rubber mount makes it worse: once the cushion is gone, the load hammers straight into the sheet metal. Stiffer shocks, solid or spherical mounts, and any track use speed it all up. Bolt a new mount to a torn tower and it will just tear again.
WARNING: If this car gets driven hard or runs anything but stock suspension, treat a torn shock tower as a when, not an if. Cars that are tracked, drifted, or autocrossed, and any car that is lowered or running stiffer springs, coilovers, or solid or spherical mounts, feed far more load into that thin tower metal and tear it out dramatically faster than a stock street car does. This is not a maybe, it is the known failure path for hard-driven E36s. Do not skip the tower inspection, and reinforce it before it cracks, not after.
With the trunk liner peeled back off the tower (Step 1), look at the metal around the two mounting nuts:
- Cracks radiating out from the stud holes. Hairline stress cracks are the first sign.
- The mount lifting, its face or studs sitting proud of the surrounding metal, or a gap opening between the mount plate and the tower.
- Torn or dished metal, actual splits or oil-canned (deformed) sheet metal, not just cracks.
- Rust at the tower and the trunk-floor seams around it, which weakens everything further.
- The rubber mount itself cracked, crumbling, or with its steel center separated from the rubber.
What you find sets the path:
- Metal flat and intact, no cracks: you're fine. Reinforcement is optional insurance, and worth it if you're going to stiffer suspension.
- Sound metal, or very early hairline cracks: add a bolt-on reinforcement plate while the mount is out. BMW's own plate (part number 51 71 8 413 359, the same one the factory later fit to the Z3) sandwiches the mount and spreads its load across the tower. One per side, two per car. Aftermarket bolt-on plates from the usual suspension houses do the same job.
- Metal actually torn, or the mount pulled through: a bolt-on plate will not fix this. It needs welding, either weld-in reinforcement plates or BMW's weld-in repair panel (left 41 14 8 169 027, right 41 14 8 169 028, though the left is getting hard to find). That is a job for someone with a welder, and it is worth doing right before the tear spreads.
What You're Replacing
| Part | Part number | Notes |
|---|---|---|
| Rear shock absorber | Standard 33 52 1 092 309 / Sport 33 52 1 090 831 / M3 33 52 2 227 794 | Splits by suspension type, not body style. Replace in pairs even if only one is knocking. |
| Upper shock mount | 33 52 1 092 362 | The rubber-and-bearing piece the top of the shock bolts to. One per side. |
| Upper mount gasket | 33 52 6 772 864 | Thin washer-gasket between the mount and the body. New on reassembly, one per side. |
| Upper mount nuts (M8 self-locking) | 07 11 9 905 374 | Two per side. New every time, the factory says never reuse a self-locking nut. |
| Lower shock bolt (to trailing arm) | 07 11 9 900 402 | M12 x 1.5 x 60, one per side, threads into a captive nut in the arm. |
| Reinforcement plate (optional, recommended) | 51 71 8 413 359 | BMW's bolt-on plate, one per side, two per car. Strongly worth fitting while the mount is out. See the shock-tower section. |
CAUTION: The rear shock splits three ways and they are not interchangeable, so figure out which you have before you order. Standard non-M suspension takes 33 52 1 092 309, the factory sport package takes 33 52 1 090 831, and the M3 (S50/S52) takes 33 52 2 227 794. There is no single "E36 rear shock." Confirm your suspension type and check RealOEM by VIN, and note the Touring wagon can carry a load-specific number worth a VIN check of its own. The upper mount, gasket, nuts, and lower bolt above are the same across all of them.
What You'll Need
| Tool | For |
|---|---|
| Floor jack plus jack stands | One jack to support the trailing arm; stands under the chassis to hold the car |
| 13mm socket and wrench | The two upper mount nuts, reached from inside the trunk |
| 18mm socket | The lower shock-to-trailing-arm bolt, the biggest, highest-torque fastener in the job |
| 16mm box wrench plus a shock-rod holder | The center rod nut is only 14 Nm, but the rod spins, so you need an oval socket (Lisle 20400) or a way to grip the rod flats. Don't clamp vice grips on the rod, you'll score it. |
| 17mm socket | Wheel lug bolts |
| Torque wrench | Final torque; the lower bolt is torqued with the car on the ground |
Step 1: Lift the Car and Find the Mounts
Raise the rear of the car and set it on jack stands under structural chassis points, never under suspension parts. The two upper mount nuts are reached from inside the trunk, up under the carpeted liner that covers each rear shock tower. Pry out that trunk liner's retaining clips and peel the carpet back off the tower to expose the nuts. On a convertible the upper mount lives in the top compartment behind the rear seat instead. The lower shock bolt is down in the wheel well at the trailing arm. One real time-saver from the DIY crowd: rather than strip all the trunk carpet, you can cut a small access flap in the carpeted tower insulation to reach the nuts. With the carpet peeled back is also your chance to inspect the tower for cracks or tearing, do that now, before you commit to the job.
Step 2: Support the Trailing Arm First
WARNING: Read this before you remove anything. The shock absorber limits how far the drive axle and trailing arm can droop. If you remove the shock with the arm hanging free, the CV joints can be damaged. Always support the trailing arm with a jack before you take the shock loose.
Put a floor jack under the trailing arm and take up the suspension weight so the arm can't drop when the shock comes out.
Step 3: Remove the Shock
From inside the trunk, remove the two upper mount nuts. If you're keeping the assembly together to swap the mount on the bench, the center rod nut is where the rod wants to spin, so hold the rod flats with the oval socket or a hex while you crack that nut. From the wheel well, while supporting the shock, remove the lower 18mm bolt. Lower the shock and mount assembly out of the wheel well.
Step 4: Install the New Shock and Mount
Fit the new shock into the shock tower using a new upper mounting gasket and new self-locking nuts. Make sure all threaded bolts, nuts, and mating surfaces are clean before assembly. Start the lower bolt and the upper nuts by hand to get everything aligned.
Step 5: Torque, Lower Bolt Last
Snug the upper mount nuts. The lower bolt gets its final torque only after the car is back on the ground at normal ride height, because the rubber bushing has to be tightened in its loaded position. Here are the figures.
| Fastener | Torque |
|---|---|
| Shock Absorber to Trailing Arm (Car in Normal Loaded Position) | 77 Nm (57 ft-lb) |
| Shock Absorber to Upper Mount | 14 Nm (10 ft-lb) |
| Upper Mount to Body (M8 Self-Locking Nuts) | 24 Nm (17 ft-lb) |
| Road Wheel to Hub | 100 +/- 10 Nm (74 +/- 7 ft-lb) |
Torque values from the Bentley BMW 3 Series (E36) Service Manual. The lower shock-to-arm bolt is tightened with the car on the ground, not in the air. Stagger your sequence so you torque it at ride height.
Step 6: Repeat and Finish
Repeat for the other side, lower the car, then torque the lower shock bolts to 77 Nm at ride height. Refit the trunk trim, torque the wheels to 100 Nm, and take a test drive over the same rough road that was knocking before.
Troubleshooting
Still knocking after the swap. Check that the upper mount nuts are tight and that you used the new gasket. A loose upper mount is the most common cause of a knock that survives a shock replacement. If the knock is still there and the nuts are tight, look again at the tower metal, a crack or tear around the studs knocks and only gets worse.
The mount looks like it's lifting out of the tower. That's the sheet metal starting to tear, covered in the shock-tower section above. Stop and sort the tower out, with a bolt-on plate for early cracks or welding for torn metal, before you rely on the new mount.
Clunk only over big bumps. Look at the rear sway bar links and the trailing arm bushings while you're back there. They make a similar noise and are right next to your work.
Ride feels harsh or the rear sits low. If you only replaced shocks and the springs are old and sagging, the ride won't fully come back. The mounts and shocks fix the knock and the bounce, not tired springs.
CV joint noise after the job. If you skipped supporting the trailing arm and let it droop, inspect the CV boots and joints. This is exactly what the warning is there to prevent.
A Note on the Upper Mounts
The shocks get all the attention but on the E36 it's usually the rubber upper mounts that knock first. They're cheap, they're right there, and replacing the shock without the mount means you'll be doing the job twice. Do the mount every time you do the shock.
Wrap-Up
Tight rear end, no knock, and a car that settles after a bump instead of pogoing down the road. While you had the rear up you got a look at the trailing arm bushings and sway bar links, so note anything tired for next time. For all the suspension fastener specs in one place, see our BMW E36 Torque Specifications guide.
Got questions? Tag us on socials or hit us at info@treedylabs.com. Show us the build when it's done. We actually want to see it.