20k seems really short to be a fluid issue...It sounds like something is actually wrong. As much as a fluid change might help, its probably not the solution. Do the obvious first and make sure its not low on fluid.

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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