Rear Differential Bearing?

Discussion in 'Modifications & DIY how-to' started by jautry27, Mar 25, 2014.

  1. jautry27

    jautry27 Member

    Ok, so for about the last 2 months, I have had a "whirring/humming" sound coming from the rear of my car. Does not change sound in turns, but gets faster and slower with acceleration and deceleration. I changed my right rear wheel bearing about a year ago, and it kind of sounds like it is coming from the left rear. I had Brandon at Allpro press out the left rear wheel bearing and he said that it didn't seem like there was anything wrong with it. I already had the parts and had driven from Covington to Alpharetta, so I told him to press the new one in anyway. Same sound still occurs.

    Could it be a bearing in the rear differential or just possibly the whole rear diff itself?

    I just put all 4 brand new tires on and that had zero effect on the sound as well.
     
  2. Matt

    Matt Think before you post Staff Member Supporting Member

    When was the last time the diff oil was changed? When my RS rear diff went out, it was making a similar noise.
     
  3. LoveMyNewSoob

    LoveMyNewSoob Member

    Not sure if it would be the same, but I had a similar noise in my old 4Runner and I ended up needing a new drive shaft and axle.
     
  4. jautry27

    jautry27 Member

    The rear was changed when I put a new motor in, which was December 2012. I used Amsoil 75/90.
     
  5. jautry27

    jautry27 Member

    I was thinking some kind of bearing. The actual driveshaft itself was my last consideration.
     
  6. crazyazn

    crazyazn I like naps Staff Member Supporting Member

    hmm i believe rear diff oil is around a 30k serivce? i tended to do it overly early but that was my ocd and the fact i used to drive the car sorta hard.
     
  7. jautry27

    jautry27 Member


    It has about 35k on it since being changed. I had planned on doing it in the next couple weeks. I didn't think going a few thousand miles over would make it do it this bad.
     
  8. crazyazn

    crazyazn I like naps Staff Member Supporting Member

    i wouldnt expect that either, however i think its safe to say it does depend on usage of the car and such.
     
  9. LoveMyNewSoob

    LoveMyNewSoob Member

    Get a quality pump! and don't get any on you!!! I made both mistakes...and paid the price... :squint: A simple job turned really annoying and smelly! hahaha
     
  10. jautry27

    jautry27 Member

    No track days. Just an occasional free spirited ride down a few dirt roads. Other than that, she never sees over 80 and rarely gets goosed at all.

    I blame whatever it is on my luck. Bought the car and had the oil pickup tube bust and cause a spun bearing within 2 days. No check engine lights or sounds to warn me otherwise.

    Within the next year: radiator, power steering pump, 3 cv axles, 2 clutches, boost control solenoid, O2 Sensor, catback exhaust (I backed into a curb and bent the resonator into the heat shield, 2 wheel bearings (only 1 ended up being necessary), and last but not least a new windshield. I can probably blame some of this on the previous owner from dogging the car.
     
  11. jautry27

    jautry27 Member

    Ok, so I've replaced the diff fluid (Amsoil 75/90) which is what I had in it before. Same noise still happening. I'm guessing at this point that it is one of several things, or as my luck would have it, all of them. Is the carrier bearing on our driveshafts replaceable? (2007 WRX) I've read where it is, but it is pressed on quite tightly and some people (forester forums mostly) have just recommended to replace the whole driveshaft. In the event that it is not that, I'm am going to assume that it is the pinon bearing or the output shaft bearings on the rear differential. Like I said before, it's a constant humming/whirring that gets faster as the car moves. doesn't really get louder or change pitch when turning, which I would assume would eliminate a wheel bearing (both of which have been changed in the last year).

    I'm also wondering if it's possibly something in the front diff that is telescoping back to the rear.
     

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