Rear Differential Bushings install Subaru WRX/STi:
This rear differential bushing install process took all of about an hour and a half. What you will need is:
I used a 3/8″ drive set
17mm Medium Depth socket
17mm Open ended Wrench
Swivel For socket (optional) i didnt need this
Torque Wrench (specs for all of these nuts and bolts are 51.6ft lbs)
Couple of screwdrivers or Pry bars ( i prefer Prybars)
Transmission lift (to hold up the rear diff when the bolts are out, you will also need this to lower the diff down to get the outside bolts over the rear axles)
Get the vehicle in the air some how, this is easiest if you have access to a garage with a lift. Which i did that only costs about $2.00 an hour. Once its on the lift go ahead and locate the area with the bolts and make sure you unplug the rear diff sensor and ground.
Unbolt the two outer nuts, you will notice that the bolt goes in from the axle side. Make sure to put them back the same way.
Now that the outside bolts are out, what you need to do it take the nuts that you have taken off from the outside and thread them over the two inner bolts that hold on the rear diff. What this does is make it able for you to take out the bolt that is directly screwed into the diff. Make sure you thread it all the way, and once they are tight, using your open ended wrench start to back off the inner nut, and it might turn a little bit without the whole thing moving but thats ok, a few turns and the whole thing will break free. ( be carefull for the rear diff sensor)
Once you get the two studs holding the rear differential in place you should be able to let down your transmission stand a little bit to move the axles out of the way and pull the studs out of the outside two bushings.