I changed the tranny fluid on my '09 RKC after about 10,000 miles following Gliders lead.:worthy I can confirm that there are noticeable improvements in shifting. It is notably Quieter and easier to shift. The shearing forces must be fierce in there! Considering the ease of changing (can be done on the jiffy stand with a quick straddle leveling at the end of draining to get the last few drops out), and the low cost, I'll always do it at 10 instead of 20,000. Cheap insurance for sure.:s I warmed it up and placed a brick under the stand to level it more before draining. Don't forget to wipe any oil off that gets on the frame under there it only takes a few seconds. Lets ride!