On my 260E by the brake pedal under the carpet there is a "hook" that keeps the speedo cable from getting caught in daily operations. Freeing it from this might do the trick.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k