2024 Subaru Outback XT first gear oil change front and back. - Notes

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Today I did the drain and fill on the front and back.
These are for the XT model the non-XT is very slightly different (tools needed drain plug placement etc)

Car was at 29600 miles, 2 years 2 months old.
it was refilled with HP diff life 75w90
theoretically 75w85 would be fine too as the owners manual allows
subaru extra MT gear oil which is a GL-5 75w80

Both fill and drain plugs are on the passenger side of the rear differential.
the fill plug is 17mm socket torque spec 36.9 ft/lb
drain plug is 10mm hex. torque spec 36.9 ft/lb
They use a reusable gasket. Both these gaskets are the same if you need a replacement.


The rear gear oil was gross "silver paint" and underfilled by 15-20% 22-23oz vs the .8L
there was a normal amount of magnet fuzz on the drain plug.
No oil leakage was evident.
I was on a slight side slope towards the fill plug side and couldn't reach gear oil inside with my pinky..
so I knew it was low before draining.. and measured it fairly accurately (funnel and jug vs drain pan)




Front diff you drain from the bottom
Drain and Check plugs are located in between the CVT Pan and the oil drain plug.
These are infamous for people draining the CVT and not the gear oil.

The check level plug is 14mm socket. torque spec 25.8 ft/lb
the drain plug is T-70 Torx torque spec 51.6 ft/lb
They take 2 more sizes of reusable gasket if needed.

I did not use the fill plug.
Purchased a 10$ "gear oil pump" from HF.
It is definitely MUCH easier to pump the fluid up the level check plug hole/tube than to get to the fill plug on top.

Gear oil was aprox the correct amount when drained. Discolored but not bad.. no silvery paint.
The check plug tube was full of crusty carbon chunks(normal for this car).. I flushed it with a couple pumps. Let drain then
refilled with 1.5qt through the check level plug and let drain until it stopped.
Drain plug with a large magnet had almost no fuzz.

The Job:
Was not too bad all the plugs came free immediately with no drama.
the most annoying factor was 4 different plug types 14mm socket. 17mm socket, t70 torx, and 13mm hex.
and re-tightening with the appropriate adapter to my torque wrench.
It is suggested to use a torque wrench as over-tightening can destroy the reusable gaskets.

Watching a youtube video on your specific subaru before doing it might be a good idea as it is very possible to drain the wrong fluid up front.



TLDR: Rear needed it.. front was probably ok for longer. ;)

The rear I will likely change again in another 15k miles.. Front will go another 30k-50k miles
 
Last edited:
With the Harbor freight gear oil pump if you remove the Hard plastic nozzle from the end of the hose
the hose fits perfectly to pump gear oil up the check plug hole into the front differential (almost perfect seal)
also works fine on the rear diff fill hole of course.

in the pic you remove the black plastic end.
I poured 4 quarts into an empty washer fluid jug that I had rinsed and dried.
the pump works with WIDE MOUTH quarts and gallon jugs (not HPL quarts :rolleyes:)
pump is aprox. 1oz per pump. easy way to figure out about when to stop.
1780524850735.webp

$10.99- Actually a decent piece for what it is.
https://www.harborfreight.com/gear-oil-and-fluid-pump-63588.html
only minor problem I had was the pump collapsed the gallon jug at the bottom and it was hard to one hand pump it while holding the hose in the check hole.
 
Both fill and drain plugs are on the passenger side of the rear differential.
the fill plug is 17mm socket torque spec 36.9 ft/lb
drain plug is 10mm hex. torque spec 36.9 ft/lb

The check level plug is 14mm socket. torque spec 25.8 ft/lb
the drain plug is T-70 Torx torque spec 51.6 ft/lb
Tangent warning!

Who in their right mind at Subaru, from the person who actually determined the torque spec, to the person who wrote the torque spec, to the editor who reviewed the torque spec and thought gee that's reasonable, would waste ANY energy writing 36.9 and not 37 or 51.6 and not 52?

So many car companies seemed focused on absolute nonsense while overlooking obvious issues.
 
Tangent warning!

Who in their right mind at Subaru, from the person who actually determined the torque spec, to the person who wrote the torque spec, to the editor who reviewed the torque spec and thought gee that's reasonable, would waste ANY energy writing 36.9 and not 37 or 51.6 and not 52?

So many car companies seemed focused on absolute nonsense while overlooking obvious issues.
(agreed)

Its likely a metric conversion their manuals and such can read as if it went through a japanese to chinese to english machine translation with no human proofreading.

36.9 is rounded from 50Nm
 
I have a 2019 WRX and was planning on doing this also. Can you fill the front differential from the vent on the top left of the diff? From what I understand there used to be a dipstick there, now it’s used as a differential vent. I was just wondering if you can fill it that way instead of using the 8 mm hex above the passenger axle.
 
Tangent warning!

Who in their right mind at Subaru, from the person who actually determined the torque spec, to the person who wrote the torque spec, to the editor who reviewed the torque spec and thought gee that's reasonable, would waste ANY energy writing 36.9 and not 37 or 51.6 and not 52?

So many car companies seemed focused on absolute nonsense while overlooking obvious issues.
I’ll only do one for you… 51.6ft-lbs is 70 N-m. That’s why they’re odd numbers.

And yes, the different sizes is frustrating. At least on the older cars all you need is your 3/8” square drive ratchet. 👍🏻
 
I’ll only do one for you… 51.6ft-lbs is 70 N-m. That’s why they’re odd numbers.

And yes, the different sizes is frustrating. At least on the older cars all you need is your 3/8” square drive ratchet. 👍🏻
I understand what they did...I don't understand why they did it.

So I'll do one for you...70 N-m is 52 ft-lbs.

I'm just asking for some common sense here.
 
I have a 2019 WRX and was planning on doing this also. Can you fill the front differential from the vent on the top left of the diff? From what I understand there used to be a dipstick there, now it’s used as a differential vent. I was just wondering if you can fill it that way instead of using the 8 mm hex above the passenger axle.
I would assume that is fine but my diff has 2 on bottom and a vent/fill on top.
Pumping it in the check level hole is much easier if you have that.

Is it a mt?
 
Today I did the drain and fill on the front and back.
These are for the XT model the non-XT is very slightly different (tools needed drain plug placement etc)

Car was at 29600 miles, 2 years 2 months old.
it was refilled with HP diff life 75w90
theoretically 75w85 would be fine too as the owners manual allows
subaru extra MT gear oil which is a GL-5 75w80

Both fill and drain plugs are on the passenger side of the rear differential.
the fill plug is 17mm socket torque spec 36.9 ft/lb
drain plug is 10mm hex. torque spec 36.9 ft/lb
They use a reusable gasket. Both these gaskets are the same if you need a replacement.


The rear gear oil was gross "silver paint" and underfilled by 15-20% 22-23oz vs the .8L
there was a normal amount of magnet fuzz on the drain plug.
No oil leakage was evident.
I was on a slight side slope towards the fill plug side and couldn't reach gear oil inside with my pinky..
so I knew it was low before draining.. and measured it fairly accurately (funnel and jug vs drain pan)




Front diff you drain from the bottom
Drain and Check plugs are located in between the CVT Pan and the oil drain plug.
These are infamous for people draining the CVT and not the gear oil.

The check level plug is 14mm socket. torque spec 25.8 ft/lb
the drain plug is T-70 Torx torque spec 51.6 ft/lb
They take 2 more sizes of reusable gasket if needed.

I did not use the fill plug.
Purchased a 10$ "gear oil pump" from HF.
It is definitely MUCH easier to pump the fluid up the level check plug hole/tube than to get to the fill plug on top.

Gear oil was aprox the correct amount when drained. Discolored but not bad.. no silvery paint.
The check plug tube was full of crusty carbon chunks(normal for this car).. I flushed it with a couple pumps. Let drain then
refilled with 1.5qt through the check level plug and let drain until it stopped.
Drain plug with a large magnet had almost no fuzz.

The Job:
Was not too bad all the plugs came free immediately with no drama.
the most annoying factor was 4 different plug types 14mm socket. 17mm socket, t70 torx, and 13mm hex.
and re-tightening with the appropriate adapter to my torque wrench.
It is suggested to use a torque wrench as over-tightening can destroy the reusable gaskets.

Watching a youtube video on your specific subaru before doing it might be a good idea as it is very possible to drain the wrong fluid up front.



TLDR: Rear needed it.. front was probably ok for longer. ;)

The rear I will likely change again in another 15k miles.. Front will go another 30k-50k miles
Interesting the that the rear diff was worse than the front? Hopefully its "broken in" and quits shedding metal. I just replaced a seeping axle seal on the rear diff on our 2.5 2018 with about 70k miles since the last oil change, and was surprised it was just a bit darker than new with minimal very fine paste on the magnet. We had got the car nearly stuck a few times over the years and my wife sometime switches traction control off, puts the pedal down and lets it spin, so there is quite a bit of 1 wheel peel on each axle, but I guess not enough to really overheat the diffs.
 
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