Rear diff leak?

So I went to change my rear diff oil for the 90k service. Noticed the thing was wet underneath, feels like oil. Not a lot, just a little. Looked like the whole differential had been wetted with oil (barely), even forward of the rear cap and fill/drain bolts. I went ahead and drained it, got at least a quart out of it (capacity is 1.1qt), so obviously it had plenty of lubrication. Wiped off the diff, then a week later, same thing, barely wet with oil underneath. Are these things prone to leaky seals where the driveshaft goes in? It's not something I've read about as a common problem on these boards. Is that a tough thing to fix? thanks for any help

Just had my 08 Legacy in for a recall on potential problem with corroded brake lines. The brakes were fine but the tech at the Subaru dealer said rthe rear diff seal was leaking. the repair involved them droping the rear diff to replace the seal, and $500 of my hard earned money. I said no thanks. I'm sure it can be done for less, and if you're ambitious you can do it yourself. As long as the oil level is ok, why worry?

It is very difficult to see where it is coming from, but I can see a drop of oil accumulates on the bolt on the bottom of the diff. Never seen a drop on the ground. I took out the fill and drain bolts, cleaned of all the seating surfaces real good, and re installed them with new gaskets...still the same leak. It's either coming from the fill bolt and dripping down that little channel, or from the bottom part of the diff cap seal, hard to tell.

 

I would say "F it, its fine as long as oil level is fine" but the only real way to tell oil level is to drain the thing out, or be lucky enough to get some out when you remove the fill bolt. Damn my car OCD...

the proper way to check the level is remove the fill plug.

 

I didn't know they had gaskets on the plugs. I thought they were basically NPT.

the proper way to check the level is remove the fill plug.

 

I didn't know they had gaskets on the plugs. I thought they were basically NPT.

 

They are like NPT, top reg. plug, bottom magnetic

Copper gasket...washer...whatever. The fill bolt had a drip of oil on it, so now I'm suspecting that. I noticed that the washer is exactly the same size as the engine oil drain crush washer, would it be bad to throw one of those on there and see what happens?

take a picture of said fill plug because we are trying to figure how your plug take a washer or gasket when there are no heads on the drain or fill plugs for the rear diff.

The spec b rear differential does have a standard drain plug that requires a hard gasket. From what I've researched and based off what the OP said, the fill plug is the same way and requires a hard gasket as well. I can't find a good picture of the fill plug though, it looks like its buried under the white line in the attached picture.

 

Picture found in this thread

http://legacygt.com/forums/showthread.php/07-spec-b-rear-diff-pics-52863.html

Yep, gaskets, check item 26 on page 3594 in the 2008 service manual. Or item 25 on the page before...

 

http://people.csail.mit.edu/ilh/vacation/

 

I normally just reuse the old old ones, I did that when I replaced the fluid at 30,000 mile on my 09 Spec B.

 

 

OP, you may have a front seal leak.

Hmm that's nice to know another thing Subaru decided to skimp on for those that didnt buy a spec b.

IMO, the NPT seals just as well and you have less parts to worry about. But I guess they figured if you can afford the Spec B you must have more money so we can sell you more parts.

 

I also understand the R-180 is used by other manufactures, so it's not like Subaru designed it for there use.

Have you used a sealer like loctite on the drain and fill plugs? Just a little on the threads of each. Get the product labeled "thread sealer". You don't want the type used to permanently install bolts etc.

SHould not need thread sealer on the R160 diff. Just snug the plugs and you should be fine.

 

If you get a little seepage, just snug it a little more.