Recommended Suspension Bushings for MN12's and FN10's

Lincoln Mark VIII

  1. racecougar

    racecougar Well-Known LVC Member

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    I was approached to write up a tech article for SCCOA on the current bushing offerings for both the front and rear suspension systems. I thought I might post this here as well.


    Recommended suspension bushings for MN12’s and FN10’s
    Written by: Rod Maksimovich (Racecougar)​

    oldbushings.jpg


    Whether you prefer a smooth, stock ride, or something a bit firmer and performance oriented, after twenty-plus years of service, all of these cars deserve a thorough inspection and possibly replacement of the various bushings throughout the front and rear suspension systems. Let’s dive right in and see what we’re dealing with, and what our replacement options are.

    Front anti-sway bar mount bushings:
    Whether we’re dealing with a stock anti-sway bar or one of the offerings from ADDCO, Energy Suspension has you covered here. They offer a channeled, greaseable, polyurethane bushing, along with mount saddles and grease zerks that is leaps and bounds superior to both the stock rubber bushings and the “hogged out” poly bushings supplied with the ADDCO bars.

    In the photo below, a 1-1/4” Energy Suspension bushing/mount is on the left. On the right is what you would receive with a 1-1/4” ADDCO anti-sway bar. If you look closely, you’ll notice that it is a 1-1/16” bushing that has been bored out to fit the 1-1/4” bar, leaving behind a rough, grippy surface without any channels for grease retention. These bushings, as well as the factory original rubber bushings, tend to squeak and resist movement. Gratuitous use of grease during assembly only delays the onset of this annoyance.
    frontswaybarbushings.jpg


    Notice the chart below, found at the following link: http://www.energysuspensionparts.com/Universal-Sway-Bar-Bushings.asp

    For the front anti-sway bar, you want to stick to the bushings in the right column of the chart. For example, with a 1-1/4” ADDCO bar, you would order part number 9.5172. If you are using a stock bar, measure the diameter of the bar with a set of calipers at the bushing location and check the chart to see if a bushing is available in the appropriate size.

    frontswaybarbushingchart.jpg





    Front strut rod bushings:
    This is one area where a higher durometer bushing material isn’t only undesirable, it can become downright dangerous. The thermoplastic strut rod to K-member bushings are known to fail without warning, which can have serious consequences.

    Just one of many reported cases of this issue: http://forums.tccoa.com/showthread.php?t=44814

    failedbushings.jpg

    I highly recommend sticking to the Motorcraft rubber bushings in this instance. You’ll need two of each of the following:

    Strut rod to K Member bushings: E9SZ-3B271-A and F7SZ-3A225-AA
    Strut Rod to Lower Control Arm Bushings: E9SZ3A140A and E9SZ3A140B

    This wonderful set of photos with part numbers was posted by Marcus at Lincolnvscadillac.com:
    http://www.lincolnvscadillac.com/fo...-LCA-s&p=2037284674&viewfull=1#post2037284674

    strutrodfull.jpg
    frontbushings.jpg
    rearbushings.jpg




    Front upper control arm to shock tower bushings:
    While there are polyurethane replacements available, this is an area of diminishing return. Provided that they are in satisfactory condition, the typical rubber bushings as provided in any replacement upper control arm assembly will perform sufficiently. If this is an all-out autocross or open track effort, I could understand switching over to poly.



    Front lower control arm to K-member bushings:
    Same as above.



    Rear anti-sway bar mount bushings:
    Just as the front anti-sway bar mount bushings, there is significant room for improvement here. These bushings host all the same issues, along with an additional recurring problem when a larger rear anti-sway bar is added to the mix.

    swaybarbracket.jpg

    When running a larger ADDCO rear anti-sway bar, broken mounts become a common problem. One solution that has worked for me in the past was to increase the thickness of the mount saddle near the bolt hole. Note the additional thickness of the mount saddle on the right side of the photo below.

    bracket2.jpg


    An improved solution is accomplished through the use of one of Energy Suspension polyurethane bushing sets along with an easily fabricated mount plate arrangement. For the rear anti-sway bar bushings, you will want to order from the left column in the chart I posted earlier. For example, with a 1-1/4” ADDCO bar, you would order part number 9.5165. Just as before, if you are using a stock bar, measure the diameter of the bar with a set of calipers at the bushing location and check the chart to see if a bushing is available in the appropriate size.

    To use the Energy Suspension bushings, you will need to create both a backing plate and a threaded plate (a nut tacked to flat stock will suffice) for each side. The backing plate will sandwich between the bushing and the IRS cradle, while the threaded plate will provide a location for the rear mounting bolt to attach to.

    rearswaybarmount1.jpg
    rearswaybarmount2.jpg


    Rear upper control arm to IRS cradle bushings:
    This bushing has a keyed, eccentric core. Rotating the core by turning the bolt securing it to the IRS cradle provides rear camber adjustment. However, this bushing is very commonly skipped over by the unknowledgeable alignment tech at the typical tire chain store. This bushing is notorious in a few other ways as well. As it wears, it allows the top of the rear tire to move inward/outward, affecting the rear camber. It often results in a “loose” feeling similar to a failing rear wheel bearing. It has also has caused some trouble due to a well-circulated replacement bushing of a flawed design. Both the correct, original design and the flawed replacement have shown up in the same packaging, under the same part numbers, through multiple brands. The only way to be certain you're receiving the correct part is to open the box(es) prior to payment and verifying visually.

    This is the bushing you DON'T want to install:
    badbushing2.jpg

    Those consist of a metal core with a off-center, elliptical, hole inside a metal sleeve which is rubber bonded to an outer shell. Turning the inner core via the bolt allows for camber adjustment, however with the sleeve bonded to the outer shell, the control arm can't move without winding up the bushing. Whoever designed/manufactured the bushing either didn't grasp or simply disregarded the original, correct design; something that seems to happen all too often when it comes to aftermarket parts. Installing these bushings results in a relatively harsh ride and very limited rear suspension travel.


    This is the bushing you DO want to install (original design):
    goodbushing.jpg

    Those allow camber adjustment and full range of motion without windup, just as they should.


    Rear lower control arm to IRS cradle bushings:
    This is one area where we can significantly reduce the vehicle’s tendency to wheelhop by changing the bushing material. Under heavy acceleration, the stock rubber bushings, along with toe link compensators that are typically past their prime, allow the control arm to deflect forward, at which point the tire breaks traction, the bushings rebound, and the cycle repeats rapidly. Removing this “give” will prevent this movement, which is a step in the right direction when it comes to reducing wheelhop and undesired rear toe changes.

    I recommend replacing these bushings with a harder material, such as the greaseable, Delrin bushings with hard anodized aluminum sleeves offered through a few individuals. Polyurethane will offer an improvement over the stock rubber bushings, however the harder Delrin material is better suited for this location.

    This is the lower control arm bushing kit that Doug (RIP) offered:
    DelrinLCA.jpg
    LCADelrin.jpg

    Photos borrowed from his website: http://home.comcast.net/~dlfraleigh/Delrin/TBirdLCADelrinBushingKit.pdf

    Rear knuckle to upper and lower control arm bushings:
    Just as the lower control arm to IRS cradle bushings, replacing the stock rubber knuckle bushings with a harder material can be advantageous. Once again, Delrin is better suited to the task than polyurethane, and a few individuals also produce a nice greaseable set with hard anodized aluminum sleeves.

    This is the knuckle bushing kit Doug (RIP) offered:
    Delrinknuckle.jpg
    KnuckleDelrin.jpg

    Photos borrowed from his website:
    http://home.comcast.net/~dlfraleigh/Delrin/KnuckleDelrinBushingKit.pdf


    Differential mounting:
    This is yet another area that deserves some attention in regards to reducing undesired movement. The stock rubber mounts allow the differential case to move significantly under heavy acceleration, especially as they age/fail. Replacing these components with a quality polyurethane will make a notable reduction in differential case movement, which is a step in the right direction. There are a number of suppliers of both polyurethane and aluminum differential case to IRS mounts. The aluminum mounts will prevent any movement of the case, however they may result in a noticeable increase in NVH.

    When it comes to the rear mount, which attaches to both the IRS cradle and the differential cover, there are a few different paths. One common, and cost-effective, method is to simply place a bolt through the rear mount, preventing the inner and outer halves from moving in relation to one another.
    02140022.jpg

    Another relatively new option is to run a polyurethane bushing in a alternative mount design, such as the one offered by Performance Art Works. If you’re handy with a welder, you can make your own at home without much difficulty using a polyurethane 4-link end and some flat stock.
    reardiffmount.jpg
    reardiffmount2.jpg

    Pictures from SCP: https://supercoupeperformance.com/partBrowser.aspx?partId=833


    Regardless of what method you choose to employ, I highly recommend either reinforcing the differential cover with a diff cover brace or replacing the cover with a sturdier version. LPW, FRPP, Fore Innovations, and Control Freak all offer heavy duty differential covers, and far, far more suppliers of differential cover braces exist.

    The LPW cover:
    diffcoverandmount1.jpg

    Without bracing or replacing the stock differential cover, you run the risk of snapping the mount right off.
    P1110343.jpg


    I hope that this short intro to MN12/FN10 suspension bushings proves helpful to you when choosing the proper replacement parts for your vehicle.
     
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    • chargerxr

      chargerxr Dedicated LVC Member

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      Good information. This probably should be a sticky.
       
    • markviiimark

      markviiimark LVC Member

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      Thanks, will come in handy.
       
    • Sapperfire

      Sapperfire Dedicated LVC Member

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      Please Sticky this!!!!!
       
    • pepperman

      pepperman The Real Deal

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      What heavy duty differential cover would fit a 95 Mark VIII ?
       
    • racecougar

      racecougar Well-Known LVC Member

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      Any of those that I mentioned will fit. (LPW, FRPP, Fore Innovations, and Control Freak)
       
    • HANG THE EXPENSE

      HANG THE EXPENSE Well-Known LVC Member

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      Most definitely.What great information.My mark is screaming for all of this.
       
    • UltimateSVT

      UltimateSVT Dedicated LVC Member

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      That's awesome stuff man. Great 411.
       
    • Silver06S281

      Silver06S281 Active LVC Member

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      wow great write up, will def come in handy
       
    • 94m5

      94m5 Dmaup's Daddy

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      Awesome Write up Sir!!!


      The Delrin rear bushings are also availible from Jeb, (lsc8) on this forum.
       
    • 98lincmk7lsc

      98lincmk7lsc Dedicated LVC Member

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      Added as a sticky.
       
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      • soduka

        soduka Dedicated LVC Member

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        When doing the strut rod to K-member bushings is it advisable to buy new inner and outer metal sleeves? Are the ones coming off probably garbage/destroyed in the process?

        Although it doesn't look like I can find them anywhere so that's a problem if I need them, guess that's why people have been making them.
         
      • racecougar

        racecougar Well-Known LVC Member

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        Only when necessary.

        Not necessarily. Even here in the rust belt, all three cars that I've replaced those bushings on have had completely reusable sleeves.

        The only sources for the factory sleeves at this point are for used parts (junkyards, people parting out MN12's/FN10's, etc.). Aftermarket sleeves can be found through a few individuals on the MN12/FN10 club forums.
         
      • 98lincmk7lsc

        98lincmk7lsc Dedicated LVC Member

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        I've taken over production of the front strut rod bushing sleeves since DLF's passing, along with just about everything else he used to make.

        $135 shipped.

        image.jpg
        image.jpg

        image.jpg

        image.jpg
         
      • soduka

        soduka Dedicated LVC Member

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        Do you have a set ready made or is it a created on demand situation? I don't want to take the whole suspension apart and then break my metal sleeves without having replacements ready. Would make my car not able to be driven for a while. At the same time don't want to spend money I don't have to. I hate these dilemmas.

        :)
         
      • 98lincmk7lsc

        98lincmk7lsc Dedicated LVC Member

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        Yep, I have that exact set, sitting on top of my tool box waiting for a new owner. The holes in the forward washers will need to be drilled a little larger to 1" to accomodate these sleeves, but that is the only modification needed. I have a set of drilled washers that I can include with the sleeves for an extra $20, but I ask that you send me your old ones once you swap them out.

        A lot of the DLF products are made to order for right now due to limited extra time, but I'm hoping to build up an inventory of parts over time.
         
      • markup97

        markup97 Active LVC Member

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        Most excellent write-up and information. Good place to start from for custom stuff as well!
         
      • markup97

        markup97 Active LVC Member

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        Ok, how about the rear cradle-to-chassis bushings? I believe I have at least one failing and need replacements.
         
      • racecougar

        racecougar Well-Known LVC Member

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        The actual rubber mounts are disintegrating, or are your stabilizer brackets just rusting out?

        attachment.jpg



        The mounts have been reproduced in UHMW, but those will increase NVH.



        .
         
      • 98lincmk7lsc

        98lincmk7lsc Dedicated LVC Member

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        I can make those as well.
         
      • markup97

        markup97 Active LVC Member

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        Stabilizer brackets are/were in good shape the last time the car was up on the lift (6,000 miles ago), so I 'Think' it is one of the bushings. I would like to get new bushings in the UHMW material, and while at it get new stabilizer brackets just to be safe.

        Thanks for the info on them, as I see that was about the only suspension bushing NOT covered in the initial write-up. :)
         
      • thaywood

        thaywood Dedicated LVC Member

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        lca bushings.jpg

        Do those bushings eliminate the toe control link?

        lca bushings.jpg
         
      • racecougar

        racecougar Well-Known LVC Member

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        Yes.
         
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        • 98lincmk7lsc

          98lincmk7lsc Dedicated LVC Member

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          Let me know. I've got the materials in stock.
           
        • achesonm8

          achesonm8 Active LVC Member

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          I am concerned about both my brackets and the rubber. My car was garaged from 1993 to 2011 so they are not in bad shape just old and tired looking! Would like to replace both the brackets and the rubber "pancakes".
           

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