rear diff leak

[awdonry]

hey guys, I recently noticed the rear half, and bottom front(drain bolt) of the rear diff is covered in fluid. the diff has about 152k kms, and had its fluid changed out 30k kms ago. (motul 300)

 

Other than the drain/fill bolts and cover, is there any other possible way it can leak?

 

Also, is 30000 kms still ok for the fluid?

[idosubaru]

you say "bottom front" but then say "drain bolt" - that doesn't make any sense since the drain bolt is on the rear of the diff, not the front. 

 

leakage points:

 

1. front pinion seal.  this is where the driveshaft attaches.

2.  side seals where the axles attach - replace seals. 

3.  rear diff plate - the entire plate the drain and fill bolts thread into mates to the back of the rear diff.  remove and reseal the plate.

4.  the drain and fill bolts could leak.  tighten, seal the threads, or replace them.

 

#1 and #2 aren't common and involve disassembling, or partially diassembling the diff to replace the seal so swapping a used unit sometimes is easier if reasonably priced used parts are available. 

 

www.car-part.com

 

that mileage is really low - except my own, most Subaru rear diffs I see go 200,000 miles with never getting changed unless it happened really early by the first owner, and i've never seen one fail, so the rear diffs are rather robust and not prone to failure, which is what we see on boards like this as well. 

[awdonry]

you say "bottom front" but then say "drain bolt" - that doesn't make any sense since the drain bolt is on the rear of the diff, not the front. 

 

leakage points:

 

1. front pinion seal.  this is where the driveshaft attaches.

2.  side seals where the axles attach - replace seals. 

3.  rear diff plate - the entire plate the drain and fill bolts thread into mates to the back of the rear diff.  remove and reseal the plate.

4.  the drain and fill bolts could leak.  tighten, seal the threads, or replace them.

 

#1 and #2 aren't common and involve disassembling, or partially diassembling the diff to replace the seal so swapping a used unit sometimes is easier if reasonably priced used parts are available. 

 

www.car-part.com

 

that mileage is really low - except my own, most Subaru rear diffs I see go 200,000 miles with never getting changed unless it happened really early by the first owner, and i've never seen one fail, so the rear diffs are rather robust and not prone to failure, which is what we see on boards like this as well. 

 

 

Sorry I was looking at it and it was infront of me so I put front. 

 

Here are some pics, pretty much the whole unit is covered. How bad does it look?

 

I think i'll park this until i get this sorted or atleast have time to check the fluid. The area where the drive shaft is has no fluid, but I will double check when I get home from work. 

 

 

 

Edited July 6, 2017 by awdonry

[Numbchux]

Yep, looks like the side seal has been leaking for some time.
 

Replacing the seal isn't a terrible job, but I would say there's a high probability that thing has run dry and likely has some internal damage. ASSuming it's not an STi, good used one is probably cheap enough.

[awdonry]

Yep, looks like the side seal has been leaking for some time.

 

Replacing the seal isn't a terrible job, but I would say there's a high probability that thing has run dry and likely has some internal damage. ASSuming it's not an STi, good used one is probably cheap enough.

 

Yeah I just noticed this during my 5k oil change. 

 

IF there is still fluid after I remove the drain plug the internal "should" be ok? If it is indeed done, I should be hearing clunking noise or none at all? Well the unit is a jdm R160 so it will be a pretty penny.

[Numbchux]

I had an r160 leak dry and seize on me. Zero notice. Driving perfectly smooth one moment, both back wheels locked up solid the next. Luckily I was carrying enough speed that I could coast/skid onto the shoulder before stopping, because it would not move under it's own power.

 

 

You may have noticed I've capitalized a few letters in "ASSuming", since you didn't bother to tell us what vehicle you're asking about. Normally I don't even respond when I have to ASSume or guess....

 

But JDM r160 doesn't mean it's special, interesting, rare, or expensive. Might be a VLSD, but those aren't rare here either.

[awdonry]

Thanks for helping. Yeah I did noticed the caps and apologize.

 

It's a rhd 98 Impreza STi wagon. So if I jack all 4 wheels up and the rear wheels still spin freely without too much effort I should be clear? I may take the advice of looking for a used unit.

 

I'll see how much fluid is left.

[forester2002s]

Check the oil level first. Take out the (top) plug; oil level should be up to the bottom of the hole. You can put in your small finger to feel inside the diff if the level is slightly below the hole. Use a turkey-basting squeeze-tool to add more oil.

Jack up both rear wheels (parking brake off). You won't be able to 'spin' the wheels, but you should be able to turn each wheel by hand. The other wheel will turn in the opposite direction. There should be no noise or grinding from the rear-diff.

Edited July 7, 2017 by forester2002s

[Numbchux]

Thanks for helping. Yeah I did noticed the caps and apologize.

 

It's a rhd 98 Impreza STi wagon. So if I jack all 4 wheels up and the rear wheels still spin freely without too much effort I should be clear? I may take the advice of looking for a used unit.

 

I'll see how much fluid is left.

 

I'm saying it may not give you any symptoms that it's damaged.

 

Pull the fill plug, and see if you can feel any fluid right there (I'm guessing you won't). Then drain it into a clean container, and see how much fluid is in it, and how nasty it looks.

 

Grab the number off the transmission (by the starter, usually starts with TZ) and google it. There are several lists online of Subaru transmission codes, and most will tell you what rear diff they have. And start shopping around.

 

The condition of the fluid and availability of a good used diff will be your deciding factors on how to proceed.

[awdonry]

Check the oil level first. Take out the (top) plug; oil level should be up to the bottom of the hole. You can put in your small finger to feel inside the diff if the level is slightly below the hole. Use a turkey-basting squeeze-tool to add more oil.

Jack up both rear wheels (parking brake off). You won't be able to 'spin' the wheels, but you should be able to turn each wheel by hand. The other wheel will turn in the opposite direction. There should be no noise or grinding from the rear-diff.

 

I'm saying it may not give you any symptoms that it's damaged.

 

Pull the fill plug, and see if you can feel any fluid right there (I'm guessing you won't). Then drain it into a clean container, and see how much fluid is in it, and how nasty it looks.

 

Grab the number off the transmission (by the starter, usually starts with TZ) and google it. There are several lists online of Subaru transmission codes, and most will tell you what rear diff they have. And start shopping around.

 

The condition of the fluid and availability of a good used diff will be your deciding factors on how to proceed.

 

I removed the fill plug while the rear wheels were jacked up, I stuck my pinky in there and there was fluid, I then lowered the car back with the fill plug still off. The fluid leaked out when the car was leveled. That means it is full?

 

I took a syringe and syphoned out 20ml of fluid and it looks the same as the new motul 300 i had laying around. I'll do a drain a fill once I pick up a new bottle.

Edited July 11, 2017 by awdonry

[Numbchux]

The fluid should be up to the fill plug (higher one of the 2), well beyond the drain plug.

[awdonry]

The fluid should be up to the fill plug (higher one of the 2), well beyond the drain plug.

 

 

sorry i was in a hurry to type that. yes its the top fill pull.

Edited July 11, 2017 by awdonry