Gen 5 Front Differential Oil Drain and Refill - Subaru Outback - Subaru Outback Forums
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post #1 of 18 (permalink) Old 03-27-2017, 11:44 AM Thread Starter
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Gen 5 Front Differential Oil Drain and Refill

Hi,

On a Gen5 Outback, how difficult is it to drain and refill the front differential fluid? While underneath our 2017 2.5i CVT Premium, I saw the T70 drain plug (off-center, slightly towards the right (passenger) side), but could not locate the differential refill and overflow opening locations. Is the refill and measurement supposed to occur via some opening in the engine bay, or is this supposed to occur underneath the car (similar to the rear differential's refill hole)? Any pointers as to where to locate the refill and overfill hole (if any) would be greatly appreciated! (@AltaBrig; has a nice write-up on a Gen4 change, but I'm not aware of a front transfer/dipstick tube on our Gen5.)

Part of my problem in obtaining a clear view was due to a large plastic 'under body' protective cover that is retained by multiple clips and at least one hex nut (unique to Gen5?). Is this 'under armor' typically removed (or at least partially lowered/disassembled) in order to drain and fill the front differential (e.g., use a Lisle clip removal tool)? If doing this work, will replacement of the black plastic clips also be necessary?

FWIW, on our 2017, I was also able to verify that:

  • the engine oil drain plug is 14mm hex (angled slightly, and accessible through a small 'under armor' cutout near the engine)
  • the CTF drain plug is 14 mm hex as well (flat on the bottom of the CTF pan -- away from the engine!)
  • the rear differential drain and refill plugs use a 10 mm hex plug head (and NOT the 13mm square plug as on other (older?) models

I'm hoping that other Gen5 owners can help steer me in the right direction to locate these fill and overfill holes, as well as what to do with the 'under armor' when attempting to drain the front differential oil.

Thanks!

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post #2 of 18 (permalink) Old 03-27-2017, 09:27 PM
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Look in the Models section (Gen 5 2015-present) and you'll find a thread on changing differential fluid.

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post #3 of 18 (permalink) Old 03-28-2017, 02:20 PM Thread Starter
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Quote:
Originally Posted by silver bullet18911 View Post
Look in the Models section (Gen 5 2015-present) and you'll find a thread on changing differential fluid.
Thanks ... I did find this thread, but no one seems to mention anything about the underbody plastic covering in the engine/transfer case area. Specifically, I'm wondering if people had to remove this, or if they simply worked around this, or if there was yet another 'trick' to changing the front differential fluid with this shield present.

In the same thread, @BHopkins also states for his 2013 Outback

Quote:
Originally Posted by BHopkins View Post
The fill is up on the driver side close to the half axle.
but (please correct me if I'm wrong) I believe that the

  • differential refill plug is on the right (passenger) side (close to the right transaxle)
  • CVT refill plug is on the left (driver) side

for US models. Perhaps I lack temerity, but I'm simply trying to ensure that no co$tly (front differential versus CVT) mix-up occurs when the time comes for our 2017 Outback ...
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post #4 of 18 (permalink) Old 03-28-2017, 02:44 PM
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Quote:
Originally Posted by mcausus View Post
In the same thread, @BHopkins also states for his 2013 Outback........but (please correct me if I'm wrong) I believe that the

  • differential refill plug is on the right (passenger) side (close to the right transaxle)
  • CVT refill plug is on the left (driver) side

for US models. Perhaps I lack temerity, but I'm simply trying to ensure that no co$tly (front differential versus CVT) mix-up occurs when the time comes for our 2017 Outback ...
I don't blame you for doing your homework. I did the same and just did the fluids last fall.
I assume you have a TR580 CVT; you can check this by popping the hood and looking on the driver side above the flywheel on the bell housing (the trans...) should be a sticker identifying the trans.

If you have the 580, should not have changed much. The CVT fill is an 8mm Allen key on the driver's side near the back end.
The differential drain is obvious. Is there not another plug about 5 inches away labelled overflow? It's an 8mm Allen key as well. The diff fill on mine is on the passenger side, near the half-shaft at a 10 o'clock position using the half-axle as a clock face. It's also an 8mm Allen key.

The tricky part is that there is some plug on the driver's side near that half-shaft but it apparently goes into the CVT fluid pump.......... So, a precaution I take is to smell the plug, pretty obvious if it is diff fluid. I was even paranoid enough that I shoved my pen light in the fill and confirmed light through the drain!
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post #5 of 18 (permalink) Old 03-29-2017, 11:47 AM Thread Starter
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Quote:
Originally Posted by mjohnson View Post
I don't blame you for doing your homework. I did the same and just did the fluids last fall. I assume you have a TR580 CVT; you can check this by popping the hood and looking on the driver side above the flywheel on the bell housing (the trans...) should be a sticker identifying the trans.
Thanks @mjohnson! Ours is a 2.5i, so it should be a TR580 ... unless we got a free 'upgrade' to the TR690!

Quote:
If you have the 580, should not have changed much. The CVT fill is an 8mm Allen key on the driver's side near the back end. The differential drain is obvious. Is there not another plug about 5 inches away labelled overflow? It's an 8mm Allen key as well. The diff fill on mine is on the passenger side, near the half-shaft at a 10 o'clock position using the half-axle as a clock face. It's also an 8mm Allen key.
Got it -- so the front differential fill plug is on the (US) passenger transaxle area, at about the 10 o'clock position; I think that part of my problem has been with all of the black plastic under cladding, it's really tough to see much of anything ... I'll have to check again more carefully for the overfill plug. (I guess your Outback is relatively plastic free underneath -- or did you have to remove this for your change?)

Quote:
The tricky part is that there is some plug on the driver's side near that half-shaft but it apparently goes into the CVT fluid pump.......... So, a precaution I take is to smell the plug, pretty obvious if it is diff fluid. I was even paranoid enough that I shoved my pen light in the fill and confirmed light through the drain!
Good idea regarding the 'smell test'; I plan on staying away from the driver's side transaxle, and since my understanding is that only the front differential has a dedicated overfill plug (unlike the CVT, which doesn't), I think that I'll be able to find the overfill with more inspection.

I'm guessing that you went with 75W-90 GL5 fluids in the front? I personally find the 2017 owner's manual confusing in this regard, and would think that (at least for a CVT-model), the front diff would be 'happier' with nominal GL5 fluid.

Thanks again!
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post #6 of 18 (permalink) Old 03-29-2017, 12:11 PM
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As a guy I don't relate well to words. I'm visually oriented aka I need a picture or two where it's clear that the drain and fill/overflow are in a single place.

In that sense I'm like Cro-Magnon man where I have this ginormous head but I need simple explanations.
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post #7 of 18 (permalink) Old 03-29-2017, 12:54 PM
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Quote:
Originally Posted by mcausus View Post
Thanks @mjohnson!
Got it -- so the front differential fill plug is on the (US) passenger transaxle area, at about the 10 o'clock position; I think that part of my problem has been with all of the black plastic under cladding, it's really tough to see much of anything ... I'll have to check again more carefully for the overfill plug. (I guess your Outback is relatively plastic free underneath -- or did you have to remove this for your change?)

Good idea regarding the 'smell test'; I plan on staying away from the driver's side transaxle, and since my understanding is that only the front differential has a dedicated overfill plug (unlike the CVT, which doesn't), I think that I'll be able to find the overfill with more inspection.

I'm guessing that you went with 75W-90 GL5 fluids in the front? I personally find the 2017 owner's manual confusing in this regard, and would think that (at least for a CVT-model), the front diff would be 'happier' with nominal GL5 fluid.
The diff fill has been on the passenger side for quite a while, whether it's was the dipstick, then breather tube, and now the solid plug. Dollars to donuts it's still on the same side. It's kind of tucked away, but if you look through the wheel well, you can see it. Oh, almost forgot to let you know that %$#@@ is on tight! It'll snap when you break it loose.
I hear Subaru put a ****-ton of plastic "guards" underneath. Probably to reduce drag and get an extra mpg or so.... I have very little "guards".
If you have an overfill plug, it should be obvious.

Technically, the CVT has an overfill, it's combined with the fill!

And yes, synthetic 75w-90 fluids. I bought 2 valvoline synpower on a US road trip (actually didn't think the units through and thought 2 quarts would do both....). Eventually I picked up a Lucas oil 75w90 for the rear (can't find VV synpower around here...), not that it mattered.
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post #8 of 18 (permalink) Old 03-30-2017, 05:28 PM Thread Starter
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Quote:
Originally Posted by mjohnson View Post
The diff fill has been on the passenger side for quite a while, whether it's was the dipstick, then breather tube, and now the solid plug. Dollars to donuts it's still on the same side. It's kind of tucked away, but if you look through the wheel well, you can see it. Oh, almost forgot to let you know that %$#@@ is on tight! It'll snap when you break it loose.
I hear Subaru put a ****-ton of plastic "guards" underneath. Probably to reduce drag and get an extra mpg or so.... I have very little "guards".
If you have an overfill plug, it should be obvious.

Technically, the CVT has an overfill, it's combined with the fill!

And yes, synthetic 75w-90 fluids. I bought 2 valvoline synpower on a US road trip (actually didn't think the units through and thought 2 quarts would do both....). Eventually I picked up a Lucas oil 75w90 for the rear (can't find VV synpower around here...), not that it mattered.
I can aver that there's a lot of black plastic underneath -- in the front and beyond, and on both the left and right sides ... A quick cursory inspection of the front plastic with my failing eyes seemed to show that most attachment points were fastened using black plastic clips, while some other points were attached with actual metal bolts. I guess that it will just be one more thing to deal with when changing the front differential, and probably the engine coolant as well ...

As for the front differential fill plug, I guess there was a lot of concern to completely seal the hole from any extraneous debris or liquid, especially with it being so near to the right transaxle area. When the time comes, hopefully I'll have enough clearance for the 1/2" drive 8mm hex Allen socket that I have ...

Many thanks again!
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post #9 of 18 (permalink) Old 03-30-2017, 05:43 PM
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The front diff goes not take GL-5 75w-90. We've been through this on the other thread previously linked.
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post #10 of 18 (permalink) Old 03-30-2017, 08:38 PM Thread Starter
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Originally Posted by BadTrainDriver View Post
The front diff goes not take GL-5 75w-90. We've been through this on the other thread previously linked.
Thanks! If I understand correctly from that thread, the specified front differential fluid is "Subaru Gear Oil Extra MT", or equivalent. Others have reported that some dealers may (or may not) sell this "Extra MT" by the bottle, as opposed to 5 gallon quantities. Some dealers may (or may not) even stock or even use (for 'in-house' service) this "Extra MT" fluid, which itself doesn't seem to be further spec'ed -- other than to say that a 75W-90 GL-5 fluid may be used, with some detraction from drivability (and no statement regarding what specific qualitative or quantitative properties would be affected).

Before doing a front differential drain and fill, I'll have to see what my local dealer says about this ...

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