‘Desert Rose’ developed a perplexing clunk from the rear that only occurred at low speeds when making a left turn onto an inclined driveway.
I had noted that the DS overslam buffer had chunks missing when the rear brake upgrade was done last July.
Since the rear was sagging, I figured the shocks and springs were worn out, allowing the car to bottom out.
I suspected that the DS rear coil may have broken from fatigue, however the coil was intact.
Closer inspection revealed that the lower ball joint on the DS connecting rod for the rear torsion bar had failed.
The untethered arm of the torsion bar would strike the backing plate for the brake rotor when the rear coil spring compressed.
Witness marks also were present on the can of the outer CV joint.
The lower portion of the connecting rod would make contact the can of outer CV joint, causing the loud clunk I kept hearing when pulling into the parking garage at work.


The ball joint rubber boots on the connecting rods for both sides all had deteriorated and crumbled away, and both overslam buffers had cracks.
I ordered two new connecting rods (MB 115-320-15-89), and two new overslam rubber buffers (MB 115-320-03-44) from an online dealership parts department (m b oem parts. com).
Four rear torsion bar bushings (MB 116-326-08-81) were ordered from the MBUSA Classic Center
(two for ‘Desert Rose’ and two for ‘Stormcloud’).

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

I chocked both front wheels and supported the car with a jack stand placed under the large bolt for the DS rear subframe mounting plate.
With the DS rear wheel removed, I was able to remove the broken connecting rod with a 17 mm wrenches.

The overslam buffer was a bit more difficult to remove.
The Allen bolt is in a deep recess in the buffer and it takes a 6mm Allen key.
My Allen socket was just not long enough, so I had to use L-shaped Allen key.
It was tedious and frustrating to try to blindly reinsert the key into the bolt after each fractional rotation of the bolt.

I used a 6-point 6mm socket on a 3/8 extension bar on the short leg of my 6 mm Allen key to get more leverage on breaking loose (and removing) the Allen bolt.
The next step was to install the new overslam buffer, which was just as onerous as the removal.
I repeated the same procedures on the PS.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

With both ends of the torsion bar free, I then removed the 19 mm bolts on the clamp that secure the torsion bar to the frame, and removed the rear torsion bar from the car.

The rear torsion bar bushing is split, with the seam pointing to the rear, and it has two ears that fit into the recesses in the body and the clamp.
The old bushings looked as if they had been. installed dry.
From lack of lubrication, paint on the torsion bar had worn away, and there were some shallow gouges also present.
I removed the loose paint with a steel brush, and coated the new bushings, torsion bar and frame recesses with Sil-Glyde.
The torsion bar was mounted back in place, making sure the split on the bushings faced to the rear.

Next, the lower ball joint of the connecting rod with its spring washer was attached to the rear axle housing.
The protective plate (MB 115-326-03-97) was reinstalled on the end of the torsion bar.
Then, the upper ball joint of the connecting rod was attached to the end of the torsion bar with a spring washer and nut.
Lastly, the wheels were remounted, the jack stands were removed, the lug bolts were torqued, and the wheel chocks were removed from the front wheels.
Now no more annoying clunk on low speed left turns into driveways.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022