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How do I know if my viscous coupling is bad V70-XC70

posted by  n1fcc on  Tue Sep 11 02:14 CST 2007
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last visit: Sun Mar 27 12:11 CST 2011
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I am replacing my driveshaft on my 1999 S70 AWD due to a bad universal. When I took it off i noticed that my back tires have flat spots. Does this mean that the coupling is locked and im dragging the tires around.

Thanks

Dave

1985 745 309k best car ever
1995 855 190k Not the best car ever
1999 s70 AWD Lemon new driveshaft, new ETM, new Bosch ABS, New Cam advance....








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    How do I know if my viscous coupling is bad V70-XC70

    posted by  KlausC on  Wed Sep 12 04:34 CST 2007
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    last visit: Fri Oct 24 10:15 CST 2014
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    I would also check the rear calipers.
    My 1998 awd has a severe rear vibration at low speed, tight turns after the car warms up. No flat spots.
    My mechanic an I are still debating, after a year, if it is the viscous coupling, the rear diff fluid, or the driveshaft. So, when I find out what kind of fluid the rear diff needs, I am going to replace it with new and see what happens.
    If the front wheels turn faster than the rear, then the coupling engages the rear wheels - both of them. It would not cause the rear wheels to stop turning. Besides, that is a lot of money for just a test. The viscous fluid cannot be replaced, according to my local dealer's mechanics.

    EDIT: Do you have a teenaged son who likes to pull the ebrake handle and slide the rear end around? :)


    Klaus

    --
    The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)








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      How do I know if my viscous coupling is bad V70-XC70

      posted by  Beaufort on  Sat Sep 15 01:21 CST 2007
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      last visit: Sun Sep 16 02:13 CST 2007
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      On my 98 XC the low speed vibration issue has never been cured despite entire rear driveline being taken apart, inpected and re-assembled. The VC is not a serviceable part so it can't be inspected. In my case the dealer removed the VC and replaced it with a new one just to check the vibration issue. In desperation, I had a vibration analysis done where they attached 16 sensors and the conclusion was 'sympathetic vibration' caused by the harmonics emitted by one or more rotating components sharing the same frame bed.
      Even though I never managed to eliminate the low speed vibration, I did manage to improve it significantly by replacing the VC's mounting bushing.
      As for flat spots on the tires, I've never seen any way to do that except by locking up the brakes. As Klaus says, maybe the hand brake is being mis-used.







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