This is a step-by-step on how remove your r160 rear-end from your Forester (or impreza) and how to replace the differential itself with a replacement, be it OE or with an aftermarket LSD.
Disclaimer: This was my first time attempting this and the information below is accurate to the best of my knowledge and I assume no responsibility for any problems or failures that you might encounter while attempting this modification.
Here's what you'll need:
A new differential
1/2" Torque wrench
3/8" Torque Wrench
1/2" breaker bar
3" 3/8" extension
6" 3/8" extension
6" 1/2" extension
12mm wrench (gear wrench is faster)
17mm wrench (gear wrench is faster)
Large Flat head screwdriver
1qt of preferred gear oil
A pump of some sort to get the oil from the bottle to the differential.
Dial indicator with magnetic base (you can pick this up for cheap at Harbor Freight)
Bearing Shim Part numbers (if you need them):
383475201 = 0.20mm
383475202 = 0.25mm
383475203 = 0.30mm
383475204 = 0.40mm
383475205 = 0.50mm
Roller bearing: 806340010 (need 2)
Axle oil seal: 806732030 (need 2)
Gasket for Rear cover: 38353AA031
O-rings: 806992020 (need 2)
Rear differential installation
Removal of Rear Differential Carrier:
1. Put rear end of car on jack stands. Chock front tires
2. Remove rear tires
3. Unhook the exhaust from the three rear hangers and let hang. This allows more working room for axle removal on driver's side and for unfastening the rear carrier from its lower mount.
4.Use a 1/2" drive (breaker bar) to undo the fill plug first, then the drain plug. Drain the differential oil into catch pan.
5.Remove the long outer lateral link bolt on both sides using 19mm socket/breaker bar/cheater pipe and 19mm wrench. One of the rear lateral links was seized onto this bolt, so I had to remove the entire lateral link to get the bolt out. Torque to 103ft-lb (The toe adjustment bolt is 21mm, nut 17mm and torque to 74ft-lb fyi)
6. I have after market bushings in my trailing arms which don't have any play so I had to remove the bolt from the rear trailing arm on each side. 17mm socket and wrench. Move trailing arm down, out of the way.
7. Now you can pull the axles out of the differential. I just used a large flat head screwdriver and pried them out. DO NOT pry using the silver metal seal cover. They will pop right out if you pry between the carrier and the green part of the axle, giving the screw driver a nice punch. Leave the outboard part of the axles in the hub.
8 Pull the axles straight out, trying not to damage the seals (unless you're going to replace them, which is usually a good idea since you're going to have everything apart)
9.I zip tied the axles to one of the lateral links, just to keep them out of the way. This will help when you lower differential carrier out of the car and also when installing it.
10. Undo the 4 - 12mm nuts that connect the propeller shaft to the front of the differential. Put the nuts, bolts, and washers aside for installation.
11. Break loose the 4 – 17 mm nuts from the studs that are pointing straight downward. Don't remove quite yet. (orange arrows)
12. There are 4 – 14mm bolts, two on each side on the lower differential mount. (red arrows)The 2 bolts on the exhaust side are a little tricky to get at, but just move the exhaust out of the way with your knee or free hand.
13. Remove the 2 17" nuts from the studs at the rear part of the case that go through those squishy bushings and connect it to the frame.
14. You may want a jack or something to support the differential case at this point. It's not necessary. I found the jack got in my way, so I just man handled it. The whole thing must weigh over 50 pounds, so be careful.
15. Finally remove the last 4 – 17 mm nuts from the studs that are pointed straight downward that you loosened in step 11.
16. The front of the differential case will now want to lower. That is okay, you will have to pull the front end down to clear the propeller shaft. Once that is cleared, wiggle the case side to side to work the studs at the rear of the case out of the bushings. Just keep shaking it side to side while pulling/pushing (depending on your orientation) towards the front of the car. It should come right out. Don't let it crash to the ground.
Voila, your rear differential carrier is out. See chapter 2 for the next steps.
**If you have an Impreza, now is the time to install those nice Turn In Concept differential bushings. Sadly, they don't fit the Forester :(. I bought them not knowing this and will have to deal with those uber squishy bushings.