(All Years) Rear differential install - Subaru Forester Owners Forum
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post #1 of 4 (permalink) Old 02-06-2013, 03:07 PM Thread Starter
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wakeabyss's Avatar
Join Date: Mar 2007
Location: Boise, Idaho
Posts: 2,885
Car Year: 2005
Car Model: Sequoia, V70R
Transmission: auto
Feedback Score: 13 reviews
Rear differential install

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
3/8" ratchet
1/2" ratchet
1/2" Torque wrench
3/8" Torque Wrench
1/2" breaker bar
Cheater pipe
3" 3/8" extension
6" 3/8" extension
6" 1/2" extension
12mm socket
14mm socket
17mm socket
12mm wrench (gear wrench is faster)
17mm wrench (gear wrench is faster)
19mm wrench
Brake Cleaner
Large Flat head screwdriver
Digital calipers
1qt of preferred gear oil
A pump of some sort to get the oil from the bottle to the differential.
Jack stands
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

Chapter 1

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.

Last edited by wakeabyss; 02-06-2013 at 06:25 PM.
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post #2 of 4 (permalink) Old 02-06-2013, 03:07 PM Thread Starter
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wakeabyss's Avatar
Join Date: Mar 2007
Location: Boise, Idaho
Posts: 2,885
Car Year: 2005
Car Model: Sequoia, V70R
Transmission: auto
Feedback Score: 13 reviews
Chapter 2
Dismantle Rear Differential:
**Helpful hint** stay organized here, keep parts together and know which side of the differential they came from.

1. Remove the brown breather cap by pulling straight up gently. It looks like it would break if pried upon.
2. Remove the 8 – 14mm bolts for the rear case cover.
3. Drain the remaining fluid out into a catch pan.
4. Use a dial indicator with a magnetic base to test backlash prior to changing out the differential. This will tell us about where we need to be after the replacement differential is installed. I measured 1/100" (.25mm) of backlash. I don't know the acceptable range, but since this is the stock measurement that I received, I'm going to assume that it is okay. Write that measurement down. After the measurement is taken, do not alter the angle of the indicator at which the measurement was taken to preserve accuracy.

5. Remove the 5 – 12mm bolts on each side of the case that secure the bearing holder plate to the carrier, which contain the axle seals, shims, o-ring, and outer race of the roller bearing.

6. Note: there is an arrow on each side of the case that lines up with an arrow on plate that houses the bearing. Make sure these align during installation.
7. Once the bolts are removed, gently pry the roller bearing plate away from the carrier on each side. Rotating it helps. When you remove the plates on each side, the differential will fall a little inside the case. Support it with your hand so that the ring gear doesn't smash against the inside of the case.
8. Note where the notch is in the spacers in relation to where they lie on the plate.
9. Keep driver's side parts and passenger's side parts separate. The spacers vary in thickness, some by 5/100 of a mm. My passenger side came with 3 spacers and driver's side came with 2 spacers. These spacers affect bearing pre-load and backlash.
10. Pull differential out, ring gear side out first.
11. To remove the ring gear from the differential, you can use an impact gun to remove the 8- 14mm bolts, or you can put the differential into a vice and use a socket and breaker bar.

12. Install ring gear onto new differential using the same bolts and torque them to 50 lb-ft in a star pattern. See chapter 3 for the next steps)

*side note: Here's a pic of a Subaru front open diff, Subaru rear Viscous LSD, and a Clutch type Diff.

Last edited by wakeabyss; 02-06-2013 at 06:18 PM.
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post #3 of 4 (permalink) Old 02-06-2013, 03:08 PM Thread Starter
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Join Date: Mar 2007
Location: Boise, Idaho
Posts: 2,885
Car Year: 2005
Car Model: Sequoia, V70R
Transmission: auto
Feedback Score: 13 reviews
Chapter 3

Install LSD into Case:
1. If you haven't already, install your new carrier bearing onto the new differential. You can use a press to put them on. I just use a pipe with the same diameter as the inner race of the bearing and pounded them on with a large hammer. Make sure they are fully seated.

2. Many LSD won't fit into the case without some minor modification. If you're using an OE replacement differential, the differential will go in no problem. For aftermarket differentials you may have to grind down the bumps inside the case on the driver's side just a little bit. You will have to grind and test a few times until you get the differential in. Keep in mind that those bumps are the outer portion of the holes that the bolts go into on the sides of the case. So, you don't want to grind too much. (obviously, when you do it, the differential won't be in there.)

3. I reused the outer races which are stuck inside the side plates. If they look bad, then they might have to be pressed in.
4. After you are able to get the differential inside the carrier without any problems, remove the differential and clean out the carrier thoroughly with brake cleaner making sure all the ground metal is cleaned out.
5. If you're replacing the axle seals, then now is the time.
6. I recommend reusing the exact spacers that were on each side. Get some digital calipers and take a measurement of the thickness of the shims for each side and jot that down.
7. Install the shims, and then place the new O-ring around the bore on each of the roller bearing plates. Line up the notches on the spacers so that they align and are in the same orientation as they were when they came off.
8. Lift up the differential with one hand and insert one of the roller bearing plates making sure that the arrow on the side plate aligns with the arrow on the case. Repeat for the other side.
9. The roller bearing plates may take some massaging and twisting to get them to seat enough to insert a 12mm bolt.
10. Thread the 5- 12mm bolts on by hand for each side.
11. Using a torque wrench, tighten to only 8 lb-ft and tighten in a star pattern.
12. Get out your dial indicator with magnetic base and check the backlash. Hopefully it is nearly identical. As said before, I don't have any Subaru FSM's and don't know the acceptable range of backlash. If the measurement is not the same, then you're going to have to move the differential one way or the other. This is done by increasing the thickness of the spacers on one side and decreasing the same increment on the other side. You want to keep the preload on the bearings the same, so keeping the total thickness of the spacers (driver's side + passenger's side) the same. For example, if you add 0.1mm to one side, then subtract 0.1mm from the other side. You will have to play around with this until you get the backlash that you're looking for. This can be time consuming but will pay off in the long run, preserving your ring gear and making things quiet.
12. It is also a good idea to check the teeth contact that the pinion is making on the ring gear. Use gear marking compound and a brush the compound on the drive (convex side ) and coast (concave) side of 3-4 teeth. (See step 2 of this chapter)
13. With resistance against the input shaft, turn the ring gear (17mm wrench helps). Make a couple passes one way, and then make a couple passes the other way.

14. Note the pattern on the teeth and compare with chart.

Here's a better, real-life chart as a pdf. http://departments.weber.edu/automot...rpretation.pdf
15. When done, wipe excess compound off.
16. Install new case cover gasket making sure that the "UP" portion is covering the breather compartment of the cover.
17. Install the rear carrier cover securing all 8- 14mm bolts to 20 lb-ft in a star pattern.

18. Install the brown breather cap by gently pushing it straight down.
19. Your rear differential is now ready to be installed back into the car. Move to chapter 4 for the next steps.

Last edited by wakeabyss; 02-07-2013 at 07:40 PM.
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post #4 of 4 (permalink) Old 02-06-2013, 04:50 PM Thread Starter
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Join Date: Mar 2007
Location: Boise, Idaho
Posts: 2,885
Car Year: 2005
Car Model: Sequoia, V70R
Transmission: auto
Feedback Score: 13 reviews
Chapter 4

Installation of carrier back into the car:
-Follow the removal process in Chapter 1, starting with step 16 and working your way in reverse to step 1.
-*If the axle seem like they don't want to fully seat into the differential, try spinning them a little. The splines have to line up just right to make it work. Also, the c-clip inside the differential might need to be moved upward to make it a little easier.
-Fill up with .8 qts of preferred lube. Clutch type LSD's require lube with LSD modifiers. Helical/Torsen differentials don't.
-Tighten drain plug to 36 ft-lb
-Break-in differential according to its manufacture's recommendations.

The end

Last edited by wakeabyss; 02-07-2013 at 07:50 PM.
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