If you've ever tried it, you already know that even after removing the bolt (under the removable plastic cover) that secures the rear wiper arm on an A6 Wagon, its still near impossible to remove. The solution is fairly straight forward. Canadian Tire sells a gear puller for about $7.50 that is fairly lightweight, but certainly sturdy enough for the job. The Audi dealer will jack you for $70 for the new arm (of course with the same crappy easy-to-break clip to hold the wiper in place). All of that said, its an easy diy job once you apply the gear puller to remove the arm off the spindle. Just thought I'd share a success.