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  • S15 Differential Noise

    I think I have something wrong with my s15 helical, but I am not sure.

    I started hearing the noise after really beating on my car at the dragon. Coming out of a turn and getting onto the throttle resulted in a noise that sounded similar to wheel hop. As soon as you backed out of the throttle, the noise went away.

    I could not see anything obviously wrong, so I just drove home. When not beating on the car, everything seems normal. No obvious noise or bad vibrations, ect.

    At a auto cross, the start was a hard acceleration into a right hand sweeper. When doing this, the noise continued to get worse. At the autocross, I noticed a movement of the passenger side output shaft that seemed abnormal. About 1mm deflection of the output flange in each direction. The output flange was fully seated in the diff.

    I drove about 100 miles home from the autox and again, noticed no abnormalities.

    Here is what the inside of the diff looks like. I cannot see anything wrong. The bearings seem fine. The fluid was not terribly dirty. I checked the backlash and it was exactly where it was originally set. It was on the high side of the spec but still within specifications.








    [IMG](http://i.imgur.com/XgLM1.jpg[/IMG]




    I will try to find a video with the noise in it. I have no idea what it could be. Is there anything inside the helical itself that could be busted? Can i even take the diff itself apart and look at it? I was too scared to take it further apart that what I have done so far since I do not fully understand how a helical differential works.
    1992 LS13
    385whp/370tq

  • #2


    This is a generic picture but the S15 is very similar. You can take it apart to see if any of the gears are chewed up. Make note of how the parts come out so you can put it back together!

    I've had one apart and it's no big deal. There aren't any springs to make it blow up when you take the last screw out...,
    Don Johnson (really!)
    Just so you know.

    Comment


    • #3
      I would also recommend to take pics of each process of undoing if you're particularly worried about taking it apart.

      Comment


      • #4
        Looks like you're spinning a bearing for some reason- I'm guessing you see it too since you focused a lot of photos on the bearing retainers. take a close look at the bearing you pulled out, and that may be your issue.
        Originally posted by SoSideways
        I don't care what color they are as long as they are LONG AND HARD.
        '04 G35 Sedan 6MT- The DD
        '96 240SX- The Track Toy

        Comment


        • #5
          I would think that it's the speed would cause an increase of the issue if the bearing housing is spinning, much like a wheel/hub bearing...
          But on the other hand, I suppose if you're stepping on it, you're applying more torque than say cruising at highway speed which has essentially zero net acceleration. I have a disassembled diff in the garage, I can snap pics of that sort of bearing cradle to see if there are marks similar to yours. I can't remember how mine looked when taking apart.

          Comment


          • #6
            when you're loading it up with torque, there are distortions that happen as well. the axle stubs don't want to spin exactly in the center of the bearing housing- they try to bend fore/aft as they're twisting. this puts lots of load on the bearings. If they're going bad or contaminated, they could be binding in certain spots on the race, thus causing the bearings to spin in the retainer and slip-grab-slip-grab etc.

            This is, of course, just a wild-ass-guess since that's the only thing I can see wrong. But my brain says that's certainly possible. could be other issues too tho.
            Originally posted by SoSideways
            I don't care what color they are as long as they are LONG AND HARD.
            '04 G35 Sedan 6MT- The DD
            '96 240SX- The Track Toy

            Comment


            • #7
              the actual rollers in the bearings look perfectly normal. There are no chips, dings, ect that I am used to seeing when I see bad bearings. I guess I will just replace the bearings for good measure, but I am basically throwing parts at it at that point. I was really hoping to see something obvious.

              I definitely saw the heat marks that appear as if the outer bearing race is spinning in the housing.

              How sensitive are s15 differentials to wheel speed differentials. The tail of the dragon has a whole bunch of cambered turns so when you are exiting the turn one wheel has alot more load than the other, causing the inner wheel to spin. This was happening alot as I was beating on it through there. Could this have caused something internally to get beat up?

              of course, for all I know it might not even be the diff. I have tried moving, bending, forcing ect everything else under there and see nothing wrong. I might try a spare diff in the car to make sure it is actually the diff since nothing in there was obviously wrong looking.

              Thanks for the input guys
              1992 LS13
              385whp/370tq

              Comment


              • #8
                What shape are your subframe bushings?
                '18 Chevrolet Volt - Electric fun hatch for DD duty!


                DefSport Koni Sleeve and Spring Perch Buy!!!
                http://www.nissanroadracing.com/showthread.php?t=5902

                Comment


                • #9
                  aluminum. also aluminum differential mounts.

                  i guess they could be worn. i will check it out
                  1992 LS13
                  385whp/370tq

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                  • #10
                    Updates? Curious about how the differential issue turned out!!
                    Originally posted by Def

                    The reason why you want signal lines as slow as possible, is that there is actually some mass flow through the signal line, enough that the cross sectional area and "long" run can cause significant minor head losses.

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                    • #11
                      Its back in the car now and i have been driving it. I didnt change anything but the fluid. I had a bad axle on the driver side but it is still making a noise. The noise is different than I remember before my hub sheared. The whine is very very loud to the point that it covers up the engine noise. I am not sure that it isnt normal, because I have had about 1000 miles on it and no issues, hasnt gotten worse, ect. My buddies all think I am hearing things.
                      1992 LS13
                      385whp/370tq

                      Comment


                      • #12
                        Well Ive had an S15 and the rear didnt make any noise. I hope you figure it out!
                        Originally posted by Def

                        The reason why you want signal lines as slow as possible, is that there is actually some mass flow through the signal line, enough that the cross sectional area and "long" run can cause significant minor head losses.

                        Comment


                        • #13
                          Mine whines on power, always has, and I've had multiple diffs in it that all sounded the same and were setup to FSM specs.
                          '18 Chevrolet Volt - Electric fun hatch for DD duty!


                          DefSport Koni Sleeve and Spring Perch Buy!!!
                          http://www.nissanroadracing.com/showthread.php?t=5902

                          Comment


                          • #14
                            If your bearing was spinning, they can peen the housing to better capture it. Have you looked at the fluid? Maybe drain a bit and see if anything looks off. 1000 miles and no clutches should mean it looks great.

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