the noises you are experiencing are probably not related to the self levelling system.you probably have some worn rubber bushings on the rear suspension.in my opinion the sls is definately worth keeping intact.just last week i took 600lb of broken tile and concrete to the landfill.you would not know that stuff was in the back

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michael cole 1980 300SD gone now but not forgotten,87tdt,90 300te 4matic 95 e320 wagon