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Discussion Starter #1
I didn’t see any comprehensive how to’s on transmission/rear differential fluid changes for 2018+ Crosstrek’s so here we go. This will be very similar to 2013-2017 models too. While I’ve never paid anyone to do car repair/maintenance, I’d estimate this will save you $200-300 doing it yourself.


Tools (outside of obvious jack stands, jack, etc.). Some differentials may have different size drain/fill bolts depending on your country.

T70 Torx bit
Long funnel
Flat head screw driver
3/8 and or 1/2" ratchet
Ratchet extension
17mm socket
10mm hex bit socket
Torque wrench (if you’re anal)
Drain pan



Fluid

Subaru’s OEM fluid is a synthetic 75W-90 GL5 fluid (part number SOA427V1700) so any brand that meets these standards will work. Crosstrek’s use an open differential so no limited slip additives are needed. If you want the best MPG numbers, OEM fluid will likely be your best bet.

If you prefer more protection for towing, etc. or longer drain intervals, you can look to the aftermarket. I chose AMS Oil 75W-90 Severe Gear so that’s what you’ll see the photos.



Before starting

Ensure the car is raised enough so you can get under it and its completely level. This is important so you can get the right amount of fluid in.


Manual transmission fluid change

CVT/Automatic owners: This won’t apply directly to you. Your CVT uses different fluid. I’d actually flush a CVT via the cooler lines and will write a separate guide if I ever work on an automatic Crosstrek. You do have a front differential (1.4 quart capacity - same 75W-90 fluid outlined above) and steps are somewhat similar in relation to where the drain and fill plugs are.

(1) Remove the intake tube on the top of the engine to locate the fill dipstick on the transmission on the passenger side. There is a plastic fastener towards the right not shown in this picture, but the head easily pops up with a flat head screw driver so you can move the intake off to the side.



(2) Under the car, locate the drain plug just behind the CV axles near the center and remove it using the T70 torx bit.


(3) Clean the metal debris off the magnet. This is what is looks like cleaned.


(4) Allow the fluid to fully drain and retighten the plug (33 ft/lbs). I didn’t use a new washer, but you can if you’d like.

(5) Add fluid and check for leaks (3.5 quarts). This has a dip stick similar to your engine oil.



Rear differential (this is for all models regardless of auto/manual transmission.)

(1) Locate the rear differential cover and remove the fill plug first as shown (I don’t have any leaks; I coat my underbody with Wool Wax to prevent rust).


(2) Remove the drain plug and allow to fully drain.

(3) Clean the metal debris off the magnet. This is what it looks like dirty.


(5) Put the drain plug back on (36 ft lbs) and start adding fluid via the fill plug until fluid slowly seeps out as shown (0.8 quarts).


(6) Tighten the fill plug (no torque specs, but it wasn’t very tight) and check for leaks

(7) Remove the jack stands and lower the car.


You’re done and just saved yourself a bunch of money.
 

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The rear differential must be different for pre 2018 models. My '19 has a 10mm allen.
Subaru used/uses 2 different rear diffs.
T type uses square drive.
VA1 uses allen.
 

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Thanks for posting. I'm going to tackle the front and rear diff fluid change in the spring. Since our MY18(has 10mm allen plug in rear diff) is only at 13k, I'll be interested to see what the fluid is like. I'll also flush the brake fluid while it's on the lift. Going to wait on dealing with the CVT.
Regards
 

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Discussion Starter #8
After about 2 weeks of sub zero temperatures (most mornings were between -5 and -10), I can say that Amsoil was a great choice. The shifter is significantly smoother and less notchy even right at startup.
 

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The manual calls for "Extra MT" in the differentials, does it not? That one is actually 75w-80 FYI.

I did also switch to the Amsoil 75w-90.
 
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