chikoo

For the history on this, see here
https://mbworld.org/forums/m-class-w...els-weird.html

Symptoms:

• Bobble head ride on uneven country roads at 45mph
• Increase in road noise, even with new tires
• Increase in vibration into passenger cabin when going over rough patch of road

Attached is an example of an uneven road patch that caused a bobble head effect. As you can see the right side is dipped about 6 inches and then evens up pretty fast. Too quick if I might say. The unevenness of the road is caused by the weight of the few heavy dump trucks that ply on this road not engineered for their weight.



uneven road

So after months of pondering on this issue, and at one point I thought I had the solution when the bushings were replaced and they were heavily greased. Turns out in 5 months as the grease dried up, all the symptoms returned.





After the grease dried up, the bushing binds with the sway bar, and it becomes part of the spring rate by acting like a torsion bar. Which is great news if you want to drive your ML350 like a tightly sprung sports car. But I do not. I want the sway bar to not become part of the spring rate equation since by design it is not supposed to. It should only come into play when cornering to prevent the vehicle from swaying around.

So this time around however, I tried something different. I released the pressure of the bushing so that the sway bar can swing freely. I did this by loosening the brackets that hold the sway bar bushing by 1/32" inch and ensuring that it stays that way by putting 1/32" shims in place.

Here are the tools I used.
18mm 1/2"-drive socket to loosen the bushing bracket bolt
24" 1/2"-drive breaker bar
2 x 1/32" metal shims (one for each side)

Hope this helps somebody.