NOTE: The "stuttering" that this DIY addresses is not chatter from the wiper moving across the glass; rather this is the motor itself moving spastically and not stopping for 3-4 cycles after the switch has been moved to "off".
First off, you need to remove the rear wiper motor from the car. This fix could most likely be done while the motor is still mounted to the vehicle, but who wants to work upside down on the tailgate? The tailgate trim is removed by carefully pulling downwards when the tailgate is open. There are a bunch of spring clips that press into slots in the sheetmetal. Be careful, and pull straight down so as not to break the spring clip mounts off of the trim.
Next, pry the cover from the wiper arm off, and use a 13mm socket to remove the nut. Before you remove the arm from its axle, mark its position with a piece of chalk or a sharpie, this will make positioning the wiper arm during reassembly a little easier. Flip the wiper arm up like you would when using a squeegee on the window, and wiggle it off of the axle.
Now disconnect the wiper fluid hose and the wiring harness from the motor. Then use a 10mm socket to remove the 3 mounting nuts for the wiper motor. The wiper motor will be free now.
Take the motor inside to your workbench or desk. Use a T-10 torx bit to remove the 7 screws holding on the silver cover. Before lifting up on the cover, pull the black nipple off of the end of the wiper arm's axle and set it aside. You'll be able to just press it back in later. Carefully pry up on the cover; be gentle and do not destroy the gasket. When the cover is removed, this is what you'll see.
Use a sharpie again to mark the position of the plastic gear. This is very important, so be as accurate as you can. Lift up on the metal arms, they are removed as one piece. Set them aside and carefully remove the yellow plastic gear. I used a pair of pliers on the ridge in the center of the gear because I didn't want to pry up on the teeth and gouge them. When the yellow gear is removed, this is what you'll see:
The two contacts circled in red will need to be cleaned, and the arms they are attached to will need to be bent up a bit. I used contact cleaner from Radio Shack, but I'm sure rubbing alcohol will work too. When bending the arms up, dont go too far; I bent them until they sat at about a 35 to 40 degree angle. The copper contact on the back of the yellow gear needs to be cleaned too because there will most likely be a ton of grease on it. Scrape the grease off and spread it on the worm gear before cleaning.
Now reassemble the motor in reverse order. When positioning the yellow gear make sure you line it up with the marks you made. Reattach the metal arms and replace the cover. Don't reattach the black nipple until the motor is mounted on the car again; when you do make sure it's pointing straight up. Be careful and patient when reinstalling the tailgate trim, you dont want to break those clips.
NOTE #2: I had to clean the contacts again since I wrote this write-up because the wiper started to stutter again.
The standard disclaimers apply to this DIY, don't come crying to me if you screw up, because this procedure worked beautifully for me and your car may vary. Good Luck!