Diff, Diff Bearings or Axle Bearings?

Discussion in 'Drivetrain, Exhaust and Electrical' started by SavetheManuals, Oct 8, 2019 at 6:18 PM.

  1. SavetheManuals

    SavetheManuals TMO Advanced

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    Trying to diagnose a new noise before I crack the diff cover (again), pull the axles, or decide if it's worth taking the car to the dealer (extended B2B warranty).
    I started to get an periodic/oscillating whir (~1Hz) when accelerating out of corners at high lat G and high load, especially in 3rd gear.
    I was in the canyons and was worried about the bearings or the diff failing so I took it easy after I started hearing the noise and did not hear it again on the drive home.
    Clearly sounded like it was coming from the rear and only happened under the above conditions.
    No leaking from the diff, axle play is negligible, no rumbling while turning, no loose driveshaft bolts, no grinding or other noises while spinning the rear wheels off the ground, and no change in diff/gear whine during normal driving.
    I do have a lot of backlash at parking lot speeds that seems to be slowly getting worse over time, and
    a high speed vibration that I have not been able to track down.
    Mostly stock Boss at 43,000 miles and 15 track days, street tires only (stickiest being NT01s), recently installed Koni Yellows, Steeda Boss Springs, Boss 302R/S trailing arms and relo brackets.
    When I changed the diff fluid a few track days ago the fluid was in surprisingly good shape and the diff visually looked fine as far as I could tell, but I have very little experience examining diffs and I didn't get the panhard bar off so I couldn't look too closely (don't worry I filled it back up using the correct hole).
    Based on when the sound occurs I'm leaning towards diff or diff bearing issue, but any other ideas or feedback would be greatly appreciated!
    Thanks!
     
  2. ArizonaBOSS

    ArizonaBOSS Because racecar. Moderator

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    Not sure, but if you're going to open the cover you might as well pull the axles and replace the axle bearings anyways.
     
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  3. TMSBOSS

    TMSBOSS TMO Addict

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    Something to think about. With the new lower control arms, axel noise will increase. You could be chasing a noise that was there all along and just not transmitted.
     
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  4. SavetheManuals

    SavetheManuals TMO Advanced

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    Fair point, but the trailing arms have been in for a long time now (just lumped it in with the other changes above for simplicity), this is definitely a completely new noise and almost definitely something starting to fail.
     
  5. TMSBOSS

    TMSBOSS TMO Addict

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    Understand. Hoping to save you some money, time.

    Have you checked end play on the axle? Could the axle shift enough to cause a noise between a single pad and the rotor?
     
  6. SavetheManuals

    SavetheManuals TMO Advanced

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    Appreciate it. Saving money and time is always a good thing! Always a good chance someone on here has an idea I haven't had or has had the same issue.

    I did check end play and it was actually less than I expected, really couldn't feel/see any play at all!
    Plus, it only made the noise on throttle, and I was definitely hitting the same lateral Gs without throttle during the same drive. I guess it's possible the additional torque could shift the axle a little more to cause the contact... but there really wasn't any lateral play when I checked. Still leaning towards diff issue.
     
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