Rear differential howling 1999 impreza outback sport

[wildernessjosh]

Hey all so this is the first subaru that i have owned and was wondering if anyone else that may have this same car or similar model has had issues with the rear differential at about 160K.

 

Its getting a little louder and i looked into it and tried to replace the oil with new oil. As life would have it the previous owner stripped out the bolt and i can't get the bottom bolt off of the differential.

 

Gona try to put a brake bleeder into the hole to siphon out he fluid and replace.

 

Words of advice and encouragement are needed so i can stop this horrible noise.

[idosubaru]

rear differential failure is extremely rare.  not impossible, but it's usually a mis-diagnosis.

 

they fail so rarely that they're nearly worthless to keep if you're parting them out and there's zero demand - so you should be able to find one inexnepsinvely used.

www.car-part.com

[wildernessjosh]

So what do you think the howling is then?

 

If it were a wheel bearing i would hear a change in the noise, a shimmy, a shake, vibration when driving car straight and moving it side to side.

 

So i ruled that out but the noise is different based on whether I'm accelerating or taking my foot off the gas.

 

The noise is def. coming from the rear under the passenger seat (its a hatchback).

[idosubaru]

 under the passenger seat (its a hatchback).

 

wheel bearing.

sit in the back to verify. you'll hear/feel it more specifically that way - though it sounds like you already are fairly sure.

 

Subaru wheel bearings routinely avoid being detected by standard tests. I don't even bother checking for play any more, it's such a crap shoot diagnosis on newer Subarus.

 

I test them after driving with an infrared temp gun - compare to opposite side - it will be notably higher than the other.  take 5 - 10

readings per side and compare high/lows/averages.  they can even avoid detection that way as well.

 

there's also the carrier bearing and ujoints in the driveshaft - but those are centrally located.

noise while accelerating/under load is often the front axle inner joint or front differential, being rear and not central rules those out.

[Fairtax4me]

When you removed the fill plug did you stick your finger in the hole to check fluid level and condition? If its low and/or dark or black and silvery looking then there could be a reason for concern.

 

Hypoid gear sets make a very distinct sound when they go bad. If the sound starts as a low pitched grumble, its probably not the diff.

[wildernessjosh]

And that my friends is why i joined this site. 

 

Gross gary i did take the car to a shop today cause one of my tires blew and had to get a new one.

 

The mechanic and i had a little chat and he is saying basically what you are saying. Its not the same type of diagnostic you would use on say a ford and since its in the back and the tires don't turn that diagnostic yes is usually out.

 

And damn i can't believe you test your wheel bearings with a infrared gun thats sick.

 

And yes the noise is all the way in the back so i m hoping for the best here bc a wheel bearing is only 23 and a used dif is about 350.

 

Fairtax i did stick my finger in the rear dif refill/top plug and the oil level was fine and was as clear as gold. And yes is sounds more like a grumble/whirring,howling sound.

 

You guys are the best and my mind is at ease a little. When i go to the shop to get my tire we are bona put it on a lift and go from there.