The first thing you need to do is remove the wiper arm. I had to use a standard screwdriver to pry mine off. After this is off there is a nut holding the housing to the lift gate¸ this needs to be removed as well. There is also a rubber washer you need to save for reinstillation when this goes back together.
On the indise of the rear hatch¸ yiu need to pull the panel off. Mine was held on with two screws in the upper corners and several plastic clips. I pull the panel away a little and look where the clips are¸ then pry them loose with a screwdrive. This is not entirely true¸ I have a door panel removal tool. It is basically a screwdriver with a notch in it that fits on either side of the clip¸ but a screwdriver will also work.
The wiper motor is held in with three small bolts and you will also need to disconnect the electrical plug.
There are four screws holding the back cover on the gearcase. I also had to remove the plastic holder for the wiring loom, this was held in place with one of the cover screws and it fit onto a tab molded on the housing. Then I opened the gear housing I noticed that the grease in the gearcase had hardened and there was rust evident all over the housing. I needed to remove the gears from the housing to clean the housing and regrease it. To do this you must drive the shaft out of the gear the wiper arm mounts to. Put some support under the gear housing¸ but to the outside so the gears will clear as they come out. The shaft can been seen in the middle of the gear¸ take a punch and drive the shaft out. The gear housing will stop the gear as the shaft is driven toward the gearbox.
After I got it all apart¸ I cleaned all the grease out and scraped the rust away. Then I took some fine wet or dry sand paper and sprayed the housing with WD40 and sanded the inside as smooth as I could.
I used synthetic grease when I re assembled the unit¸ because that is what I had. I put a lot of grease in the hole for the shaft to help prevent water from going down along the shaft and into the gearbox again. I supported the under side of the gear with a block when I tapped the gear back onto the shaft before I put the geagcase cover back on.
Installaion is just the reverse of removal¸ don't forget the rubber gasket on the outside of the shaft. Before putting the wiper arm back on¸ turn the wiper on to be sure the gears are back at their starting position (When you had the case apart you did notice the electric contacts in the case and on the plastic gear didn't you?). Now put the wiper arm back on and test your motor. I had to move the wiper arm a couple of times before I got it on in the correct position.
After this my wiper has worked perfectly. I hope yours will as well.