rear diff, axles or what?

Discussion in 'General Motoring' started by dean, Apr 19, 2005.

  1. dean

    dean Guest

    Any advice on what could be wrong with my 96 Legacy Brighton based on the
    following description?

    When I go in reverse and turn sharply, for example to parallel park, I can
    hear a shudder and the car behaves as if it had hexagonal wheels: it jerks
    and hesitates to roll. I can't really tell if the noise is coming from the
    front or the back. Driving in the city and on highway I did not notice
    anything weird with the drivetrain (doesn't pull to one side and it makes no
    noise when turning in the streets). To get more details on the problem, I
    did the following test.

    1. if I go forward (on an empty parking lot) and turn the wheels all the way
    to one side I can make 3 or 4 full circles without any problems but after
    that, the car starts exhibiting the above mentioned jerking and shudder
    similar to what one experiences when a front axle is gone bad on a FWD car.

    2 if I do the same, but going in reverse, I can also make a few rounds with
    no noise or problems but after the 5th turn the shudder and noise increase
    to the point that one can barely drive the car. It rolls very rough, it
    produces an awful sound (as if something is being ground down), brutal. It
    even stalled on me once as if I had a parking brake on. After doing several
    circles and upon hearing and feeling this problem I stopped the car and got
    out (wheels fully turned), only to see that the car jerks forward (slightly)
    about every second. I could hear something turning and hitting in the same
    rhythm as the car was jerking. As soon as I straightened the wheels and
    drove straight, the noise and roughness was gone.

    Could this be a worn/bad axle and how would one figure out what side and if
    it is front or back?

    Could it be the differential? Front or back? How to tell/test?

    Anything else that could produce the above mentioned symptoms?

    Please help with your advice before I turn to the dealer for
    inspection/repair.


    (My Legacy is AWD, 2.2l, 173k km, manual(clutch near the end of its life),
    front right axle replaced more than 50k km ago, front diff/trans oil changed
    10k km ago, rear diff not checked recently)
     
    dean, Apr 19, 2005
    #1
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  2. I had the same problem with a 95 Legacy L at just over 150k miles.

    It was the center differential which is AFAIK not a separately
    replaceable/rebuildable part from your manual tranmission. I replaced
    the entire assembly with a used one from the junkyard - parts and labour
    just under $1000 US.

    What happened is that the viscous coupling - a clutch pack of several
    disks embedded in silicone - has burnt out either by reaching its
    'natural' end of life or by some sort of asymmetry in your car's drive
    train.

    E.g. This usually happens when people run on their doughnut-size spare
    for too long and too fast.

    florian /FFF/
     
    Florian Feuser /FFF/, Apr 19, 2005
    #2
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  3. Something to check before replacing transmission....

    Newer subies do that if there is not proper tire inflation. Even 4 pounds
    lower on one side will make that happen. Check your air first. Something
    about the limited slip stuff having "give" for turning that gets over worked
    if the tires have different radius.
     
    Sparky Polastri, Apr 19, 2005
    #3
  4. Good point - I may have been wrong to assume that the OP made sure to
    have equal pressure in all tires. Another thing to consider is uneven
    wear - this could give away any existing asymmetry in the drive train.

    My 95 Legacy tires were shot when I bought the car; the car was crabbing
    sideways and fishtailing pitifully. The tires may even have caused or
    accelerated the failure of the clutch pack.

    In any case, if the problem really only occurs after doing a few donuts
    at max steering angle, it may be futile to worry about it. After all,
    the center differential is SUPPOSED to bind under certain conditions
    when "slippage" [read: different RPMs at the wheels] occurs.

    In my experience, the car would bind after any prolonged drive,
    especially in turns after a stretch of highway driving.

    good luck

    florian /FFF/
     
    Florian Feuser /FFF/, Apr 20, 2005
    #4
  5. dean

    dean Guest

    Thanks for your input...

    I always make sure the tires are inflated to spec and I often check the
    amount of thread left on them. This is in part due to several posts I read
    on this subject back when I bought the car. I never used the small spare
    tire (it still looks very new) nor let anyone tow my car with only two
    wheels jacked up. The car does not have a hitch so it never towed a trailer.
    I do not do any offroading.

    That said, then it could as well be the center LSD(limited slip diff). All
    in all, I am a bit surprised that a center differential would burn at 170k
    km. It is possible that the first occurrence of the problem happened to me
    almost a year ago. After a 4 hour hwy drive I was pulling into a U shaped
    driveway when it happened: binding and grinding was horrible. After the car
    cooled down and for the remainder of the trip, this had not repeated and
    therefore I kind of forgot about it thinking it might be due to the CV
    joint. But when you said the same thing happened to you after a long drive I
    remembered that incident. Since that trip, my wife drove it mostly to work
    and back (20 km commute) so there was not really a chance to experience it
    again.

    Anyway, I did call Subaru and got a quote on the replacement of LSD that is
    definitely making me think about the other option suggested in some posts on
    this subject - just continue driving it. If the LSD fails (presumably the
    silicone liquid inside lost its viscosity), can I then ignore the problem
    and drive the car with a bad LSD? If it is bad, is it in "open" or in
    "locked" mode? If "open", will it behave as a FWD such that rear wheels
    don't get any power from the transmission and do the front wheels 100% of
    the power in that case? If "locked, is it still AWD?

    too many questions, I know...

    thanks for your advice, I will continue investigating on NG and USMB...

    regards
    Dean




     
    dean, Apr 21, 2005
    #5
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