Torn diff bushings

Discussion in 'Transmission & Drivetrain' started by moffetts, Mar 28, 2020.

  1. moffetts

    moffetts Well-Known Member

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    I've been chasing an intermittent clunk in the rear end and I either found the culprit or I found an unrelated problem; at the very least, my drivers side rear diff bushing (OEM) has a big gap in it where the rubber has given up. Apparently this is fairly common, based on what I have read. Now the question is, short of replacing the entire subframe to get new OEM bushings, what is the least-NVH adding option to rectify this? This is an 80/20 street/track car and I'm fairly anal about added NVH, so I am trying to assess my options. Looks like I could go the BMR BK049 or Steeda equivalent poly lockout route, but that seems to add a noticeable amount of NVH, especially with me having a 3.73 rear end. Another option would be the Whiteline KDT933s, which are new bushings entirely and therefore have a higher installation overhead/cost, but they are softer and theoretically more compliant and less likely to transmit NVH than the poly lockout options.

    Are there any other options I'm not thinking of? And regardless of which route I go, should I be looking at the BMR bolt/hardware upgrade as well?
     
  2. Burkey

    Burkey Well-Known Member

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    Having used both the BMR lockout and the Whiteline KDT933, I’m going to say just go the Whiteline direction.
    They will add a small amount of NVH, but nothing even close to what the lockouts add.
    I would replace the bolts that come with the kit though.
     
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    moffetts

    moffetts Well-Known Member

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    Thank you sir, that does appear to be the best route at this point.
     
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  4. Cdnspeed

    Cdnspeed Well-Known Member

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    i replaced my subframe, my bushing was completely torn through and it wouldn't make any difference if i had used an insert as the metal sleeve would still move in the torn bushing.

    I bought a whiteline kit KDT933 but never installed it, if you're interested in it shoot me a DM
     
  5. AlbertD

    AlbertD Well-Known Member

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    I've been down this road... went with the BMR BK049 and absolutely hated all the clunking noises I was now able to hear from the drivetrain. The whining was also quite loud at highway speeds for a street car. I ended up taking the entire subframe out and replacing it with an new OEM one. I ran a through bolt setup in the OEM rubber bushings as well. I'm hoping that delays accelerated failure of the bushing again, but don't have enough time with this setup to know if it will help. My car had 50k miles and a ton of track time when my driver side bushing went out.

    My advice... replace with OEM if you are concerned with NVH otherwise, you may be left disappointed.
     
  6. AlbertD

    AlbertD Well-Known Member

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  7. BmacIL

    BmacIL Enginerd

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    Did you get the sleeves put into the rear bushings to take out the ~3 mm oversize hole on the bolt?
     
  8. AlbertD

    AlbertD Well-Known Member

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    I made my own makeshift setup from hardware I found at Ace since I was in a time crunch. So no sleeves, but the bolts I found took up most of the slop within the bushing. It isn't perfect, still probably have ~1mm or so gap. When the rubber bushing goes out again, I will most likely have retired the car from daily duty and will just go solid at that point. I do really miss how the IRS felt with the poly diff and delrin subframe bushings. On track feel was amazing.
     
  9. BmacIL

    BmacIL Enginerd

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    I'm fairly convinced that the premature bushing failures are from that oversize hole. You can see evidence of marring from the threads of the bolts smashing into them. Impact loading is bad...

    Do you have any sort of subframe isolation parts now? I was shocked how much just the BMR CB005 did for rear end feel and confidence.
     
  10. AlbertD

    AlbertD Well-Known Member

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    At this point, nothing. I have gotten used to the way the car feels out on track in stock form and enjoy having a quiet rear end. I may pick up something in the future if I find a good deal on one of the bolt on solutions though. Like you, I was also surprised at how much more composed the rear end felt after I went poly/delrin and love it out on track... the NVH was just unbearable for me as a daily. I realize the bolt on solutions are more forgiving as far as NVH and provide 90% or more of the benefit so I may try them out one day.
     
  11. BmacIL

    BmacIL Enginerd

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    Definitely. Very little NVH worsening with what I mentioned. I've had it on for ~55k miles.
     
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    moffetts

    moffetts Well-Known Member

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    The KDT933s are already on their way, so we shall see how this goes.
     
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    moffetts

    moffetts Well-Known Member

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    Got the RH017 hardware in today and I am confused as to how this is supposed to work. Step 9 of the instructions for RH017 state to "thread it [the shortest of the three included lengths of bolts, pictured] into the front side of the diff bushing" but I don't see how that is possible with aftermarket bushings like the Whitelines. Thread them into what? The bushings are just two pieces of hard rubber with an unthreaded metal sleeve in the middle. image0.jpeg
     
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    moffetts

    moffetts Well-Known Member

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    Well crap. I think the rear bolts are still usable, at least.
     
  15. Burkey

    Burkey Well-Known Member

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    I’m trying to recall exactly what I did. All I recall is that I literally replaced the supplied Whiteline bolts for same length etc.
     
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