Get the rear of the car safely up in the air. Put the car in gear, and block the front tires just to be sure. As shown in the pic below jack up the car by putting the jack under the rear diff.
Place jackstands at the jackpoints just in front of the rear tires (there's a cutout in the sideskirt for this) and lower the car onto the jackstands, but do not remove the jack as you will need it later on.
Slide under the car and take a look at how the rear diff attaches to the mount.
There are two double ended studs toward the middle that attach the mount to the rear diff. There are two bolts (one at each end) that go through the subframe and through the bushings in the mount
All nuts and bolts are 17mm.
Liberally spray the studs and nuts for the bolts with PB Blast or your equivilant, and drink your cup of coffee while waiting for it to soak in.
On the STi disconnect the rear diff temp sensor and ground by pressing on the tabs for the connectors and pulling them off
Using your open ended wrench to hold the bolt head (it's behind the axle) and your 17mm socket remove the nut from the bolts at each end.
You will not be able to remove the bolt because it will be blocked by the axle, but we have a way to work around that.
Take the nut from each bolt and thread it onto the stud.
Tighten these nuts down so that you have now double nutted the studs. This locks the original nut in place so you can back the double ended stud out of the rear diff. If you don't do this, and just try and back out the stud using the single nut you MIGHT get lucky and back out the stud, but make life easier on yourself and follow our tip to double nut it.
Now, here's the tricky part. Using your open ended wrench put it on the original nut by sliding the end of the wrench between the rear diff mount and the rear subframe.
Being careful to not round off the nut, back out the stud. It'll take some effort the first time, and remember "Lefty loosey, rightey tighty."
On the STi be VERY careful about the rear diff sensor.
Once you have the stud out you will notice that the threads for each end are different. Course threads go into the rear diff and fine threads are for the nuts.
Once you have the studs out use the lower the jack a few inches. The rear diff and axles will lower allowing you to slide the bolts out of the mount and rear subframe.
Once you have the bolts removed slide the rear diff mount out of the subframe and take it to your workbench.
Now for the removal of the bushings. We also have a couple of alternate techniques so check below on those
Using your fairly strong buddy or a c-clamp secure the rear diff mount to your workbench. Tony's kind of a wimp so we used the c-clamp (He claims he is He-Man, Master of the Universe, but notice we still used the c-clamp).
Now, take your couple of screwdrivers and shove them between the stock bushing and the metal of the mount. The easiest place to do this is where the voids are in the bushing. Be sure to put the drivers between the bushing and the metal NOT through the voids.
Once you have the screwdrivers inserted pull on one, and push on the other.
Then reverse the push/pull. Once you have loosened the bushing take your hammer (or whatever you choose to push the bushing out) and shove on the center of the bushing.
We have found a strong steady push works best instead of small shoves.
Do this for both ends of the mount.
Alternate technique 1
Use a press to press the bushings out. By far this is the easiest way, but not everyone has a press.
Alternate technique 2
Take a big socket and put it on the ground.
Put bushing over socket
Stomp on mount next to bushing
Bushing should pop out and bounce around the garage
Laugh as it bounces around
Repeat for other side
Now that you have the stock bushings out of the mount take a moment and finish your coffee while staring in amazement at the wimpy stock bushings.
Take your new beefy TiC rear diff bushings and do the following:
Take a look at the mount. On one side in the middle will be an arrow.
When you reinstall the mount the arrow will be pointed UP and will be the side AWAY from the rear diff.
Slide back under the car and push the mount up into the subframe.
It will take some shoving because it's tight with the new bushings.
Take a look at where the bolts go through the subframe and through the bushings. It'll look something like this:
Since everything, including the sleeves for the bolts, is such a tight fit you'll need someway to line this up.
Use one of the screwdrivers through the hole for the bolt to get things lined up for one side. Do this by wiggling or levering as you need.
Slide the bolt into the hole. When inserting the bolt do it just like the factory and install from the axle side.
Repeat this for the other side of the mount.
Jack up the rear diff until the holes on the diff line up with the holes on the mount. Try and avoid using the screwdriver thing if you can since the stud holes are aluminum.
It'll take some wiggling and jacking up and down, but you'll get it.
Take the studs and start to thread them in.
Thread in all the way, and tighten down as best you can. Your socket with the swivel can help here.
Now, using your open ended wrench to hold the original nut, back off the extra nut for the bolts.
Torque spec on these is 51.6 lbs, but it can be a bit hard to get a torque wrench on there so you may have to do it by feel.
Take those nuts and thread them onto the bolts. Torque for these is also 51.6 lbs (from the service manual).
On the STi be sure to reconnect the ground and rear diff temp sensor.
Safely get all four wheels back on the ground, and go for a spin.
After that make yourself a sandwich since that's all you've been thinking about since you pushed the bushings in.