What to look for in used differentials?

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  • bmp
    Member
    • Jan 2005
    • 81

    #1

    What to look for in used differentials?

    Looking to buy used differentials and was curious what to look for when buying used ones. Wouldn't want to have it installed and find it starts humming after only 20,000 miles of use.

    Thanks.
  • Danny
    Moderator
    • Feb 2008
    • 14217

    #2
    Make absolutely sure that they spin.

    Comment

    • Adrian_Visser
      R3VLimited
      • Jun 2006
      • 2823

      #3
      make sure there is fluid in it






      jk it may be hard to tell if the output shaft bearings humm unless the diff is in the car and spinning at speed under load.

      '89 Alpine S52 with goodies

      Comment

      • rThor432
        No R3VLimiter
        • Feb 2007
        • 3907

        #4
        If it takes 20,000 miles for a diff to start making noise, there wouldnt be a problem when you bought it.

        Best thing to do would be to pop the cover off and see what it looks like inside. You can check the backlash on the ring gear, but that's about it really. You wont get any noise out of the bearings without loading them up. If you do, dont buy that diff.

        For limited slip units you could check the break-away torque of the different output shafts to check the condition of the clutches.

        Comment

        • Wh33lhop
          R3V OG
          • Feb 2009
          • 11705

          #5
          My diff whines :( I've heard that all the LSD units tend to whine. That doesn't make much sense to me but my buddy got his S4.10 rebuilt and his definitely whines (then again he has no sound deadening).
          paint sucks

          Comment

          • rThor432
            No R3VLimiter
            • Feb 2007
            • 3907

            #6
            My limited slip units dont whine.

            Comment

            • h82crash
              Advanced Member
              • Feb 2008
              • 127

              #7
              The LSD is not whining, the bearings or gears are. If it makes ANY hissing noise turned by hand, it will in the car. Grab both flanges and turn as fast as u can. Also should be silky smooth, no notchyness.
              "Life is hard...it's a lot harder if you're stupid."

              Tom
              72 2002
              87 327i
              88 525i
              88 535i
              03 530i

              Comment

              • Holland
                R3V OG
                • Nov 2008
                • 7176

                #8
                Cool, nice to know.
                1985 M10b18. 70maybewhpoffury. Over engineered S50b30 murica BBQ swap in progress.

                Originally posted by DEV0 E30
                You'd chugg this butt. I know you would. Ain't gotta' lie to kick it brostantinople.

                Comment

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