Thread: DIY: Subframe Bushing Install

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  1. #1 Post DIY: Subframe Bushing Install 
    Join Date
    Feb 2007
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    Woodstock, Ga
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    Special thanks to "SyDeWaYz" on 240sxforums.com

    http://240sxforums.com/forums/instal...-anti-56k.html


    To end all discussion, i decided to do this. Basically this is the thread to end all threads as they pertain to subframes. Any questions about phantom "clunks", wheel hop, ect. should be directed here, although wheel hop is also largely attributed to blown shocks)
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    So you bitches want to rid yourselves of that clunking sound in your rear? You ever hear a phantom BOOM when u come off the brakes or downshift hard? How about when you go over a rough bump? Yes? Then you need to read this mofo right here, probably the most in depth, percise, lenghthy noob oriented guide ever written in the history of 240sx forums.com (as of 2/20/2006).
    ************************************************** *****
    If you know everything about what that problem is and why it’s happening, skip to the installation guide. If not, a little background on what’s up:
    ************************************************** *****

    Most likely, your problem is partially, if not wholly attributed to a loose subframe. The subframe is a HUGE metal assembly present in the rear underside of your car which basically links your differential, driveshaft, rear hubs, shocks, control arms and whatever other suspension pieces you can shoot off the mouth.

    The subframe, ideally, being that its such a critical component in your rear suspension, should be attached directly to your chassis and bolted down with lots of torque right? Wrong. If this were the case, you would experience numb nuts on a daily basis. The ride would be so rough and full of vibrations…well let’s just say that for a car on the American market 15 years ago….the 240 wouldn’t have made it to the streets. For the track yes. For the streets…..meh.

    So Nissan decided to use rubber bushings to bridge the metal to metal connection. We all know the properties of rubber, and why in the daily driver’s eyes, rubber was the way to go. For performance, rubber provides a slow response to extremely sharp moments due to the length of time for the material to compress. But Nissan built this car for comfort and reasonable stock performance, hence the name “Sporty Coupe”. One thing Nissan either didn’t consider or didn’t care about was the fact that over time, rubber components in any structure that is repeatedly exposed to any extreme amounts of heat, moisture, drying, vibration and time will eventually deteriorate and fail….looking like this:




    So the bushings die, and the subframe begins to “swim” when you shift the momentum (inertia) from the front to the back of the car (i.e. releasing the brakes, downshifting, etc.). Thus the resulting *clunk* is from the subframe contacting the differential/drive axle/chassis in a way it really shouldn’t (not sure exactly what hits what).

    A lot of people try to use spacers to solve this, like these:



    but, it’s only a temporary fix which results in the above bushing destruction anyway.

    Solution: Polyurethane or solid replacement bushings.

    ~Polyurethane: a really tough plastic alloy (lol) that reduces compression time and will completely eliminate the clunk. Also improves drift performance.
    -Pros: ^^^^^
    -Cons: Like rubber, it won’t last FOREVER. For most of us, the 240sx will be a toy for the next 5-15 years or so, so they will outlast your love for your 240sx.

    ~Solid Metal Bushings: MEH, they’ll also eliminate the clunk, but they are solid metal, so things like vibrations, bumps and road noise will be attenuated. (Reduction in ride comfort). I cannot comment on the severity, but from what I hear it’s not too bad.
    -Pros: Best for performance, basically like a directly bolted subframe. Bushings will outlast you.
    -Cons: Ride quality is deteriorated.

    The choice is yours, and yours alone, and the process to replace them is the same either way. Now on to the install. WOW, that’s a long explanation eh?

    Installation Guide:
    The method I’m using requires the burning/cutting of the old bushings. If you can get your hands on a Bushing Press (ask around at car stores), all power to you.

    Parts:
    (1) Energy Suspension Polyurethane Subframe Bushing Kit for 90-96 300zx z32
    Part Number: 7.4102 ES
    (2) Four [4] M12 X 1.25 metric nuts
    Cost: $65-$100

    Required Tools:
    1) Decent socket set, preferably one with ½ inch drive…the bolts are seriously torqued down hard. ($50-100, pepboys)
    2) 14 mm wrench to detach driveshaft from differential ($7, Lowe’s).
    3) Burning tool (Blow torch) ($16, pepboys)
    4) Cutting tool (sawzall or dremel) ($50, pepboys)
    5) Hydraulic jack ($20, Wal-Mart/pepboys)
    6) At least 2 jack stands ($10, Wal-Mart)
    7) Wheel blocks (bricks- 2 @ $5, lowe’s)
    Drill with 2” wire brush bit. ($6, pepboys)

    Tools that will make life easier:
    1) A friend ($Cost of lunch, life)
    2) Urethane safe grease ($2-MPL from Advanced Auto will work, just ask for MPL)
    3) Breaker bar ($25, lowe’s)
    4) A second hydraulic jack or a Trans jack. (no idea how much trans jack is)

    If you are a complete n00b to car stuff, and you have no tools whatsoever, this project will total up to about $368. Quote from my mechanic, $118 of labor + bushing cost = $215, but the average place will quote around $260.


    On to the install.
    1- Jack the rear of the car up. Ensure to place the car on jack stands and block off the front wheels to the car doesn’t roll and kill you. NEVER work under a car which is supported by improper equipment. An ok setup:



    2- The first thing I would do would be to go ahead and remove the tires. Once the tires are removed, go ahead and remove the brake calipers, as well as the rotors. There are two bolts attaching the calipers to the hubs, located behind the calipers. You are going to need to remove the ebrake from the caliper by removing a 14mm bolt on the side. You also want to remove a 10mm bolt securing the ebrake cable to the actual subframe itself. Once the caliper is properly detached, go ahead and zip tie it to something, example:



    3- Next step would be to unload the shocks from the hub assembly. Now it helps to have a friend to do this, but basically you need to remove the 17mm bolt behind the shock/ hub connection, and pop the shock forward. Have a friend push down on the hub and u can easily remove it. After “unloading”:



    4- Once you do that you want to work on the differential. Remove the 4 14mm bolts that fasten the differential to the driveshaft, as illustrated here:



    5- To remove the subframe, you’re going to have to remove the exhaust. This actually sounds worse than it is, it takes about 8 minutes. Basically, you want to remove the metal bends that are secured by the rubber hangers, I believe there are 4, 3 of which are easy to remove:



    You might want to support the rear of the exhaust before doing this as to not overstress the connection to the cat. The last one is one that’s tough to get out due to all the pressure, so I just removed it completely, by loosening one 12mm bolt, and removing the bracket assembly:




    6- Basically the last thing to do is to remove two bolts that attach to the side of the catalytic converter closer to the engine. Once that’s done the exhaust will drop, and if its stock its pretty heavy: Out on the ground:





    7- Were about ready to start on the subframe. Before you do anything, remove the ground screw and rubber pipe (air?) from the top of the differential:



    Once those are removed, jack up the differential to relive pressure off the large 19mm nuts you are about to attempt to remove.



    8- To remove the subframe, there are a total of 8 bolts to attack. 6 in the front (closest to engine) and 2 in the rear. Start by removing the two bolts that secure a “L” shaped bracket in the front, they are 14mm:



    Ok….that being done go ahead and remove the large bolt supporting the subframe. Breaker bar helps a lot here (pic is after the initial loosening):



    9- The front bolts are the last thing to remove to get this bad boy out. After removal:



    Now once you do this the jack is the only thing supporting the subframe. SLOWLY lower the subframe to the ground, and remove from under the car. This takes skill; I used two jacks and basically pulled it out on wheels:



    10- So you got the PITA out eh? Gets worse. But before that we get a little pyro fun. Time to blaze this bitch up. Basically, follow the directions on the blow torch and use it to burn out the rubber. Most likely it will ignite:




    11- Ok so there’s only so much you can burn out. Once you have burned out most of the front and rears, the part that sucks starts. You’re going to have to remove ALL the rubber in each hole. Begin with the fronts (as in front of the car). There is, unfortunately a metal ring (actually there’s two) that you need to remove. Using a cutting tool like a sawzall, you need to make a cut through both rings, but do NOT cut through to the actual subframe. Look at my cut depth:



    12- Make this cut on both sides of the ring. Once completed, you should be able to jam a screwdriver into the space between the two rings, and remove the INNER RING, using some strong pliers. Its very hard to see, but this is it once out:



    13- You need to now remove the outer ring. This is a PITA. If you can’t get it to start peeling and bending, your cut may be too shallow. You need to be able to do this:



    Try not to cut the lower ring. I couldn’t avoid it, but this is my finished product for the fronts:



    14- Now for the rears. First take a sawzall (if you have it) or a knife, and begin to thin out the layer of rubber remaining:



    Then, use a screwdriver and the wire brush bit on a drill to clean out the front holes:



    And you should get this:



    This is friggen hard to achieve, so be prepared to waste at least an hour on this step.

    15- Using a knife, you need to remove a small layer of rubber under the each hole in subframe so that it is flush:



    16- Once you finish step 15, you have gotten through the hard part. Using some MPL or some other urethane safe lubricant, grease up the bushings and insert them in the subframe as shown in the instructions you should have gotten with the bushings. (Large one thru the top, metal rod through the middle, small piece on the bottom). To get them in without damaging them, I did this:



    -Yeah I’m a pretty small guy, but I got heart and love for my 240. If I can do it you can do it.-

    17- You’re not done yet. As you probably noticed, the z32 bushings don’t go all the way in, and are a lot taller the stock (bout half an inch). You’re going to need bolts with more threading to re attach the subframe to the rear chassis, the ones you removed only yield about 2 turns, which is uncool and unsafe. Now I personally shopped around for some new m12 X 1.25 metric bolts to no avail. Here’s the best, and free solution. There are multiple suspension pieces fastened to the subframe assembly that have the same bolt size and threading as the bolts you need. Half of them are just like the ones you took off, and the other half don’t have the lip, and are more rounded. You basically want to find 4 (two from each side) of the rounded bolts, remove them from the suspension pieces, and use the subframe bolts in their place. I took 4 of these (doesn’t matter where you get them from):



    And replaced them with the previous subframe nuts:



    Once you have 4, you’re done.

    18- Now you can go ahead and raise the subframe back into the car. This will be tough and probably will require a friend or 2 jacks, or both. Once up, reattach using the newly retrieved bolts. Should look something like this:




    Proceed by reassembling your car, and don’t forget the ebrake cable, the (air?) rubber tube and ground wire for the differential. Don’t reattach your exhaust just yet. Just for kicks once everything else is back on, and the car lowered to the ground, try and start your engine and see how sexy she purrs. It’s nice, and worth a listen, but very loud, and very illegal, so don’t drive or anything….lol. Well once the exhaust is on your done. Once you test drive it and ensure there are no problems, take it in for realignment. You should immediately notice you no longer clunk, and that the overall response and behavior of the car, especially the rear, is more concise and controlled. Excellent. Yes, polyurethane owns.
    Last edited by Casey; 03-22-2009 at 12:18 AM.
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  2. #2  
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    Good write-up. Huge PITA.
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  3. #3  
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    yeah im going to be doing the poly bushings on my coupe.

    if its running by the install day ill do it then
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