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2017 Subaru Forester 2.0XT
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Discussion Starter · #1 ·
Hi folks:

I took the front diff plug as I’m making the front diff oil change. I’m not sure how this crush washer is supposed to be installed or if I even got the correct one.
Please let me know, seeing the photos attached, if I got the right one (803926090), how to install it and if I have to look up for the old crush washer. I know it’s a trivial question, but the crush washer seems quite small for this plug.
 

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18 Forester 2.5
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5 Posts
Hi folks:

I took the front diff plug as I’m making the front diff oil change. I’m not sure how this crush washer is supposed to be installed or if I even got the correct one.
Please let me know, seeing the photos attached, if I got the right one (803926090), how to install it and if I have to look up for the old crush washer. I know it’s a trivial question, but the crush washer seems quite small for this plug.
You got the wrong one, that looks like an oil drain plug gasket washer.

What was on the diff plug when you took it off? Without looking it up, I didn't believe the front diff had a crush washer, I thought it was a flat steel/rubber lined washer that just provided a seal.

Also, make sure you torque to proper specs, under torquing is not good and neither is over.

Please keep us posted :)
 

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2019 Forester Limited
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Best bet is to ask your Subaru parts department for the correct washer, rather than guess poorly. You’ll need to show him which plug it’s for on the parts diagram. He likely won’t know if you show him the plug in your pics. My ‘19 uses crush washers all around. Edit: not all are crush washers.


The one you have likely fits the fill plug and the level check plug on the front differential. I think what you have in your hand is the drain plug. Going from memory.

Oddly enough, I had to hit up three dealers to get the full complement of washers for front and rear differentials.
 

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2020 Sport
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308 Posts
The T70 plug is bigger in dia. There are plenty of threads here discussing that. Mr. Subaru‘s UT video has front diff fluid change demo on a crosstrek that share the same part.

Here you go:
Fluid: 75W-90 GL-5, 3 quarts

Front: 1.5 Q, Rear: 0.8Q (approx.)

Tools: 10mm Hex, 8mm Hex, T70 Torx, Regular Hand Tools
Breaker Bar, Extension, Transfer pump, Drain Pan

Supply: Gasket 803918060 X 3
Gasket 803926090 X 1
Optional: Brake cleaner, shop towel, Torque Wrench and wire brush

Torques: For 10 mm and 8 mm plugs: 37 ft-lb
For T70 plug: 52 ft-lb
 

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2011 Subaru Forester
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While I know it's best practice to replace gaskets, is it always necessary? Aren't these all basically washers rather than o rings? I would think they can be reused, and my guess is they usually are. I also thought we should use oil-resistant thread sealant on the plugs when reinstalling. I will try and have a look at the Mr Subie Crosstreck vid.
 

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I appreciate the big picture thinking, but it doesn't really address the specifics. Also, we are talking about the transfer case and rear differential, not the transmission. Simple fact is that metal washers rarely fail. The biggest risk of failure is more likely to come from forgetting to reinstall it. Side note it's interesting that the torque values are 32.5 ft-lb for the aluminum washers and 51.6 for the copper or black metal ones, and no thread sealer is required for the front diff. There are no gaskets to replace for the rear but both fill and drain plugs require thread sealant to be applied.
Maybe it was changed after my 2011 but I don't see any talk of replacing crush washers in the rear in the factory service manual
 

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2022 Forester Limited 2018 Forester XT
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Its a soft Iron gasket. I don't see it in the picture. Maybe it is still attached to the differential. It does not need to be replaced...if its the same as my 2008 NA
 

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While I know it's best practice to replace gaskets, is it always necessary?
Of course it’s necessary.

I think what you’re really asking is if one can save a couple bucks by reusing the gasket and sometimes get away with it. Sure, but why do that? False sense of frugality? Feeling smarter than the manufacturer?

Compared to the engine, differentials and transmissions can’t have their fluid level as easily inspected or topped off, and the change interval is much longer. A small seep adds up over time.
 

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2015 Forester 2.5i Limited CVT
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The gaskets go over the threads.
I replace them all. They’re inexpensive and if you go through all the trouble of changing gear oil, why not?

The diff doesn’t hold much oil and any leak could become a problem. I’m sure that an old used gasket will hold, but only if it’s less than 40k miles old. Time will make them brittle also.
 

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2017 Subaru Forester 2.0XT
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Discussion Starter · #13 ·
You got the wrong one, that looks like an oil drain plug gasket washer.
Yeah, I think I got the wrong one.
This crush washer seems like the same the engine oil plug uses.
Since the washer or gasket didn't came loose after I removed the drain plug, I was confused on what to look.
I checked the drain hole and didn't saw anything. It was just bare metal, with a bit of rust in the outer edges of the opening. I was expecting something to fall, stick to the drain plug or maybe have a different color, texture or material.

Finally I cleaned the drain plug and installed it as I found it; obviously, without the washer I bought.
I torque it to spec (51.6 ft-lb).

I was able to replace the overflow/check plug gasket; it was a black one. Also torqued it spec (25.8 ft-lb).
 

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Discussion Starter · #14 ·
Best bet is to ask your Subaru parts department for the correct washer, rather than guess poorly. You’ll need to show him which plug it’s for on the parts diagram.
I should have show them the diff plug, rather than asking them to give me both washers for the front diff.
This is what they gave me at the dealer, but they might been wrong with the drain plug one
 

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Discussion Starter · #15 ·
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Agree, both took around 2.2L of gear oil; I used Motul Gear 300.
My diffs do not use hexs, since mine is the XT. I used 14mm for front diff overflow, T70 for drain plug, and 13mm square for both rear diff fill/drain plugs.

I was able to squeeze the bottles by hand for the rear diff, although I had to use two bottles, because they didn't empty completely, although it required around 0.8Q. For the front diff, I used a long funnel and filled it through the rear passenger side of the engine bay.
 

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@[email protected]
Agree, both took around 2.2L of gear oil; I used Motul Gear 300.
My diffs do not use hexs, since mine is the XT. I used 14mm for front diff overflow, T70 for drain plug, and 13mm square for both rear diff fill/drain plugs.

I was able to squeeze the bottles by hand for the rear diff, although I had to use two bottles, because they didn't empty completely, although it required around 0.8Q. For the front diff, I used a long funnel and filled it through the rear passenger side of the engine bay.
Yes, I was citing a late model TR580 tranny for Crosstreks and Foresters.
in the shop manual by SOA for diff and CVT fluid changes. All procedures ended with “use a new washer.” Just sayin’
 
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