A friend wants to buy a 2001 Legacy wagon (MT) whose owner may not have kept the differential oil level topped off.

What are the symptoms of a diff that's been run on low oil level?

grinding,howling,jerking,clunking,buzzing,thumping..... was it really ran that low? if so a replacement may be in order, or just try draining it out and putting fresh oil in.

Low oil usually results in a whine at first which gets progressively louder. If it's not making any obvious noise, drain and re-fill and you should be good to go; it only takes about one quart of gear oil.

damn can't find my pictures.. but what has been said above.. I blew my front diff because it ran low.. i started hearing it howl on the highway.. so I pull off at the next exit.. tried to make it to the dealership or autozone but taking off at no more then 5% throttle it blew up pretty much in the worst sound you ever want to hear and split the case as that...

 

diff oil was all over the place.

 

 

I don't think it can be saved if it was howling and I refilled it with fluid? Nevertheless I miss the forester.

 

Found them

 

Edited December 29, 201015 yr by 1-3-2-4

it takes more than 1 qt of oil, I believe the front,well in my 97 takes 7.4pts, and the rear is 1.7pts.

What I'm wondering to myself is: What would cause the diff to be low on oil? Most owners never touch the diffs, so unless there's something previously broken and it's been leaking, one would normally expect them to be factory-full.

 

As an aside, if you're going to change the oil on both diffs (assuming an A/T), just buy 2 quarts of oil. The one takes slightly more than a quart, the other slightly less, but it all comes out about a wash.

What I'm wondering to myself is: What would cause the diff to be low on oil?

Taking it to Jiffy lube for an oil/trans fluid change.

 

 

The front differential shares fluid with the transmission on the MT. So if the diff fluid was low, the trans fluid was really low and you have much more to worry about than the diff.

 

Rear differential hardly sees any load, so if it was low just drain and refill it some some good synthetic gear oil. Worse comes to worse you have to replace it, which isn't that hard, and you can usually get one from a U-pull for under $100.

 

Now for the all important question: What symptoms lead you to believe that either differential is damaged?

The OP said it was an MT, manual. Do you mean the rear diff, or the transmission? The front diff is part of the transmission on the manual, so the front diff shares the gear oil for the gearbox. So if the oil level is good for the transmission the diff should be alright too. You have to run them pretty low for a long time before blowing it up.

 

With the rear diff, it probably isn't low unless you see signs of leakage. If in doubt, pull the top plug out and stick your finger or a stick in there to see where the level is. Should be about the same height as the top plug.

Yeah, the Sube in question's got a manual gearbox so, of course, I'm referring to the aft diff.

I crawled under the back end and tried to loosen the upper plug but couldn't. Used a 1/2" breaker bar but wasn't able to get enough leverage to get the plug going.....not enough clearance. Guess I'll have to raise the back end.

Sure wish Subaru used the same type of plugs on the Gearbox and diff as are on the oil pan.....six sided bolt heads instead of those four sided inverted ones.

It 'd make things easier.

The gal who's selling the Sube said she's always had the lubricants tended to by various oil change outfits, which is why I'm focused on the diff gear oil level.

Can't trust the dudes that are employed there to do careful work.

I always have a hell of a time getting diff drain plugs out... Spray it with PB blaster or some penetrating oil and let it sit for a while might help. But what I usually resort to is putting my 1/2" breaker bar in the plug. Then taking the spare tire jack and jacking up the breaker bar to loosen the plug. On my car it was so stuck this actually lifted the whole back end off the ground!! But some jumping on the back of the car broke it free and the plug came right out.

... wasn't able to get enough leverage to get the plug going...

 

Keep trying to remove the upper plug.

 

You've probably thought of this, but whatever you do, DON'T remove the lower plug first, as that will allow the oil to drain. Then how will you refill the diff with the upper plug in place?

Then how will you refill the diff with the upper plug in place?

 

Take it off and flip it over

Keep trying to remove the upper plug.

 

You've probably thought of this, but whatever you do, DON'T remove the lower plug first, as that will allow the oil to drain. Then how will you refill the diff with the upper plug in place?

 

Well, duh!

I had to use a 3 foot pipe on the handle of my breaker bar to get the fill plug loose on mine. And even then it still didn't want to come loose. The drive popped out of the plug twice.