I would have to go back and look to be sure, but I thought that the top nut is the adjuster which lengthens the stem, the bottom one is the lock nut. If I am right, and I wouldn't bet on being right until I look at it again, this does not change the length of the spring. I'm now very anxious to go take another look.

Good luck,

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Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles