15 Front Diff Fill Plug STUCK!!!

Using a standard 8mm hex key that fits in the space without much extra room I'm UNABLE to get the fill plug to budge even a little. What did you guys who have replaced your front dif lube do to get it loose?

I'm going to by an 8mm hex 1/2" drive and hope it's just long enough to give my 1/2" drive breaker bar some room to break this thing loose.

Note: I'm not talking about the T70 drain nor 8mm overflow plugs. This is the plug on the side of the diff, above and to the left of the passenger front drive shaft.

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Sidenote: the rear diff plugs came off, no problem. I'm letting the rear diff drain as I type this. Before this I finished replacing the front/rear diff oil in our '14 FXT, which was MUCH easier!!!! The FXT doesn't have an under tray with a dozen clips to remove and DOES have an easily-accessible breather tube to use for filling.

Read this thread: https://legacygt.com/forums/showthread.php/front-diff-fluid-change-275863.html

Note the three plugs and manual description.

Also here: https://legacygt.com/forums/showthread.php/front-diff-fluid-change-275863.html

Sometimes a bit of heat to the plug will help -- ensure it's clean to the bottom as well.

I read those as a reference, but they don't help my situation.

Also, there's a lot of rubber and plastic in the vicinity, so heat is problematic.

Using a standard 8mm hex key that fits in the space without much extra room I'm UNABLE to get the fill plug to budge even a little. ...

I don’t like your chances with a standard hex key if it is that tight. Hex keys also try to twist at an angle if a lot of force it applied. Your idea about the hex drive socket & breaker bar should work.

But if it doesn’t, ‘plain OM’ on subaruoutback.org forums posted a good idea a fair while ago for removing a tight plug from the rear diff. It involves the use of a bottle jack. See post #2. But I wouldn’t use a jack with a standard hex key.

Using the weight of the car when jacked up is another way. See UKPR1’s post #14 in another subaruoutback.org topic.

BTW - I haven’t tried either of those methods, so I don't know how safe they are.

Can’t use a jack in this instance. The exhaust (specifically the cat) runs just beneath this area. I’m going to buy a hex impact socket and an extension and see if I can finagle my breaker bar past either port or stbd side of the cat.

Using just a 10mm hex key I was able to loosen both rear diff plugs BY HAND! I was thrilled.

I had to use a breaker bar on our 14 FXT, it was so tight. The difference, I think, is that the FXT has pipe threads (and likely sealant), while the Legacy has straight threads with a gasket on each plug.

Can’t use a jack in this instance. The exhaust (specifically the cat) runs just beneath this area.

I see your problem. Perhaps try a few light taps with a hammer on the end of the plug to see if it jars it enough (if you have enough room). I’ve used that method on tight bolts before, but I would advise having a thick piece of aluminium, copper or brass held against the plug so the hammer doesn’t directly hit the plug & cause any damage to the plug.

I see your problem. Perhaps try a few light taps with a hammer on the end of the plug to see if it jars it enough (if you have enough room). I’ve used that method on tight bolts before, but I would advise having a thick piece of aluminium, copper or brass held against the plug so the hammer doesn’t directly hit the plug & cause any damage to the plug.

I did try this, as well as two types of penetrant (PB Blaster and Deep Creep) without any success. My next post will explain how I succeeded.

The winning combination pictured below: 14" 1/2" drive breaker --> 1/2" to 3/8" drive adapter --> 8mm 3/8" drive hex key

-----I had the Craftsman breaker, purchased with points before all of the local branches when under

-----I picked up the adapter and hex socket from HF

I tried to open-palm the breaker bar as much as possible, but still managed to slightly bust my pinky knuckle as the plug let go with loud POP!!!, ripping way a 1/4" of skin in the process...

The next hardest part was getting the diff full and THEN lifting the car to re-install the overflow-check plug. I had to lift the rear up and shimmy under, since the overflow/check plug is on the rear driver-side of the front diff. I knew I was on the right track when I began to lift and the slight dribble through the port, indicating that the diff was full, completely stopped.

MAN DO I MISS HAVING ACCESS TO A LIFT!!! The Forester front diff was MUCH easier to do, because the fill port is the vent port, which requires pulling a vacuum-style hose which is connected via o-ring seal only. There's also so much clearance that I didn't have to lift to vehicle to shimmy under and re-install its overflow/check port.

I posted pics here at BITOG (you'll notice that post looks pretty darned similar to this one lol)

-----You can hose pics on BITOGs servers, which saves me time from having to go to tinyurl to do so here...

https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/5377943/re-8mm-hex-impact-1-2-drive-suggestions#Post5377943

I also want to note that the 15 Legacy FB25 front diff did not take as much fluid as the 14 FXT. The 14 FXT actually took slightly more than 1.5 qts. The Legacy took ~1.25 quarts, maybe a little less.

I was worried, because I only had 1.4L (1.48 quarts) of Motule Gear 300 and, like I said, the FXT took a little more than 1.5 quarts to fill. I had half a quart left of M1 w/ LS additive, but really didn't want to mix gear oils. I'm sure it would have been fine, but having a complete fill with just the Motul gear lube would be ideal, which is what ended up happening anyway!

Good to see you got it done. Going by your photos it does look pretty tight in there.

I found the low height of the Liberty (Legacy) was also a hassle whenever I had to work underneath. It made me appreciate our previous SJ Foz XT for that.

As for the front diff oil quantity differences. Perhaps the quantities in the Owner’s Handbook (see below) are only approximate figures seeing you had slight variations to these.

Front diff quantities from the respective Owner’s Handbooks:

MY13 SJ Foz XT - 1.4lts (1.5 US qt). - fitted with TR690 CVT.

2015 Legacy 2.5i - 1.2lts (1.3 US qt) - fitted with TR580 CVT.

2015 Legacy 3.6R - 1.4lts (1.5 US qt) - fitted with TR690 CVT.