Rear diff or rear axle?!?!?! please help. - Page 2
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This is a discussion on Rear diff or rear axle?!?!?! please help. within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Found out its not the diff. My LSD 3.90 diff spun the rear tires when I did the little test. ...

  1. #16
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    Found out its not the diff. My LSD 3.90 diff spun the rear tires when I did the little test. One wheel started moving a little ahead of the other one, just like it should (seeing its an LSD). Any ideas on what this can be, I'm stumped. The one person that came over to look at my car, said it was the clutch. Can it be?

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  3. #17
    Registered User Obeisance's Avatar
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    Perhaps the next thing to try would be to get a friend and to both try to turn the rear wheels (together, same direction when it's on the jackstands)? I assume that since this is all wheel drive that you should not be able to turn the rear wheels (when the front is on the ground) if the drivetrain aft of the center differential is in good working order. If they turn then the problem is at or after the center differential... (I'm not too familiar with the mechanics of this car, but does my logic make sense?)

    ..although, I suppose the fact that the rear diff spins the wheels in opposite directions kinda confirms that it is solidly connected to the center diff.. right?
    Last edited by Obeisance; 05-07-2012 at 06:31 PM. Reason: Afterthoughts

  4. #18
    Registered User Ingen's Avatar
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    I'm thinking you busted something in the clutch, but that's just my swag-style guesstimate, and I'm no expert. I don't suppose you smelled any clutch burning smells on the way home?

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    Quote Originally Posted by Obeisance View Post
    Perhaps the next thing to try would be to get a friend and to both try to turn the rear wheels (together, same direction when it's on the jackstands)? I assume that since this is all wheel drive that you should not be able to turn the rear wheels (when the front is on the ground) if the drivetrain aft of the center differential is in good working order. If they turn then the problem is at or after the center differential... (I'm not too familiar with the mechanics of this car, but does my logic make sense?)

    ..although, I suppose the fact that the rear diff spins the wheels in opposite directions kinda confirms that it is solidly connected to the center diff.. right?
    Do you mean turn it by hand?..... I did something like this yesterday, I tried to move the rear wheel with by hand and it wouldn't move. So then I went ahead and put the car in first gear and slowly released the clutch, then this is when the rear wheels began to move.

    The only weird noise I noticed is a weird squeaking noise (like when squeezing a toy) just when the car begins to move.

    -- And no, I did not smell any clutch on the way home.

  6. #20
    Registered User Obeisance's Avatar
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    I did mean turn by hand... i misunderstood the above post (where you tested the LSD), but am now a bit more confused. Am I correct in understanding that you had the rear of the car on jackstands, the front on the ground- then you put the car in gear and allowed the engine to turn the rear wheels?

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    Yes, your correct.

  8. #22
    Registered User Obeisance's Avatar
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    On to another question, based on my understanding, the center differential should be a viscous differential and it should not happily allow very much movement of the rear wheels without movement of the front wheels. When you engaged the clutch slowly do the rear wheels spin freely or did the car feel like it wanted to drive off of the jackstand?

    What I am getting at is this: I think that troubleshooting this problem may need to involve holding two of the shafts constant in each differential (front, center and rear) with the ground or something similar and trying to turn the third. It seems that you have done this test in a few different ways by now:
    1 - holding front and rear wheels while turning at the engine - no coupled motion = broken between wheels and transmission/clutch
    2- holding front and engine while turning at wheels (by hand) - no motion = okay connection (or not enough torque) - rear diff is well connected to center and to whatever makes them limited-slip
    3- holding front and turning engine - coupled to motion at rear - okay connection between transmission and rear diff (assuming that the speeds scale properly)

    What happens if you repeat these tests with the front in the air? (for this you can engage the e-brake to make sure that the rear will not roll) Can the front wheels turn by hand or with the engine?

    also, if you're feeling like taking a risk, you should be able to see the rear driveshaft spinning under the car...

    I think that my suggestions may just be my curiosity and may be a dangerous waste of time... I have had my car up (front and rear passenger side were lifted) to switch the uppipe and have had either the front or rear up to paint brakes or change oil, but I don't remember being able to turn any of my wheels by hand (i think that my 05 wrx has open front and rear diffs, but I still couldnt easily turn the wheels by hand in the air).

    [aside]... I'm beginning to realize my logic errors now... my understanding is that in any differential the three shafts are mechanically connected and thus if you hold two of them then the third is also fixed (or if one of them is held then the other two should be coupled in motion). Thus, in my previous suggestion if anything can be turned by hand (assuming that the transmission/clutchplate is fixed to a fairly immobile engine) then any component of the drivetrain at or after the clutch may be broken even with the front wheels fixed-> my suggestion was not going to be helpful for troubleshooting.

  9. #23
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    [Just for an update]:: car has been fixed. It turned out to be a broken front axle, the outer cv boot did not burst. Instead it broke inside so when I accelerated the car the inner part of the axle will spin the boot like when twisting a shirt. So somehow it did not allow power to the front two wheels.

  10. #24
    Good news, everyone! xxxxxxxAnub1s's Avatar
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    Glad you found the issue man, and that it was a relatively cheap fix.
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    Good news, everyone!

  11. #25
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    Quote Originally Posted by Obeisance View Post
    I did mean turn by hand... i misunderstood the above post (where you tested the LSD), but am now a bit more confused. Am I correct in understanding that you had the rear of the car on jackstands, the front on the ground- then you put the car in gear and allowed the engine to turn the rear wheels?
    Quote Originally Posted by OutFittedWRX View Post
    Yes, your correct.
    For future reference, this is not something you should EVER do. Ignoring how unsafe it is, it's massively bad for your center diff.

    Glad you found the problem and hope you learned your lesson about not launching these cars.
    Scott
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    Quote Originally Posted by teflon_jones View Post
    For future reference, this is not something you should EVER do. Ignoring how unsafe it is, it's massively bad for your center diff.

    Glad you found the problem and hope you learned your lesson about not launching these cars.
    Thanks, and yes I really did learn my lesson about not launching these cars. Hopefully others can learn from my mistake. I would not be doing this again, even when I get the r180 diff.

    #LessonLearnedTheHardWay

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