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e30 rear subframe bushings-replace or leave

Discussion in 'E30 (1984-1993)' started by 02m3smg2b, Jun 7, 2010.

    02m3smg2b guest

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    I have a 87 325is, I am replacing the driveshaft and flex disk due to vibrations. Driveshaft is off and new on is here to install, While I am "in there" should I venture to replace the sub frame and trailing arm bushings? I have not had any issues...but well.. I have so much out of the way it may be a good time to do this, and replace those brake lines under the sub frame too (i have stainless elsewhere). If I am going to do this are the race bushings (Like the IE Blacks) going to be so harsh that I will not want to drive it on the street? This is mainly a DE car that I drive to and from the track, but I do some about town driving too.

    Thoughts and recommendations are appreciated

    I am an intermediate DE student doing 3-4 events per year.
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    MGarrison

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    I presume you're replacing the drivshaft support bearing as well - kinda a no-brainer if you're doing the other rubber bits there.

    Replacing the rubber subframe bushings is not an easy diy job. You'll likely need a press to get new rubber ones in. I have the Ireland Engineering green mounts, which (according to my mechanic) installed fairly easily - those added a good bit of interior noise to the vehicle, but not intolerable. I wouldn't go with race bushings if you want to keep the car reasonably streetable.

    You have the exhaust and driveshaft off - so as to whether it's worth it at the moment, depends on how much of that you want to get into again. Otoh, if you have the money & time now, then why not - old parts aren't going to get any newer.

    With the driveshaft off, dropping the entire rear suspension assembly is pretty straightforward - unbolt the shocks from the trailing arms, disconnect the appropriate brake line(s), use a jack or two and some boards carefully positioned to support everything, and the entire rear subframe/trailing arms/diff will drop right out when you pull a diff-support bolt and the rear-subfram-bushing nuts. If you're gonna go that far, that would certainly make access to the trailing arm bolts a snap.

    Access to the various hard brake lines would never get an easier, so if you do that, it's worth replacing any lines if they have rust bubbles. BMW lines don't come pre-bent, so save the originals to duplicate the bends as exactly as you can (and keep them in their original shape), and if you can find a pipe-bending form of small enough size, that can be helpful - some of the bends are pretty tight and it's easy to crimp the pipe instead of getting the bend you want. The little screws that hold the plastic clips over the brake/fuel lines can be rusty and impossible to remove without breaking. Be cautious, consider the stuff for unfreezing rusty parts (PB-Blast, etc?)- unless you want to weld new mounts on, or drill the underside of the car, there's no convenient way to secure the plastic clips if you can't remount in the original locations. Coat whatever screws you put back w/ never-seize to hopefully waylay that issue in the future.

    The apparent downside to the offset-bolt type of camber-adjustable trailing arm bushings is keeping them tight (and thus your suspension in proper alignment), at least until they're so rusty they're frozen in place (& thereafter risky to try adjusting without breaking an offset bolt). Otherwise, you have the weld-on slotted tabs that allow for a large range of adjustment. Presumably, not being an offset bolt, those may hold their position more tightly. Or, use oem or urethane, non-adjustable. If you don't go for the adjustable tabs, then it's not a bad idea to reinforce the weld on the trailing arm tabs. Mine had only a spot weld on one side and had enough stress over many years of events to end up cracking the weld, making the car rear steer. Welding the tabs on both sides to the trailing arms took care of that.

    And if you're going to drop the subframe, you may as well get the various diff seals replaced and throw in some fresh diff fluid - Redline; you may need the lsd friction modifier as well, not sure but you can research that and find out.

    02m3smg2b guest

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    I will proceed to replace

    Thank you fpr the reply, I'll think I will march on with this project and order the green (street) IE sub frame bushings, diff mount, and the urethane traling arm bushings,

    Had not though about the diff seals, good idea.

    I appreciate the advice.
    • Member

    MGarrison

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    Glad to be of help; a minor correction - I meant to say in the post you can drop the whole rear suspension assembly when you free the rear-subframe-bushing nuts, and the diff-bushing bolt. I edited the post to say what I meant, instead of the trailing arm bolts - obviously you'd leave the trailing arms attached until you have the subframe free. Be careful, obviously the subframe/diff/halfshafts/trailing arm assembly is very heavy, bulky, and awkward once freed from the car.

    Fwiw, I've kept the stock solid-rubber bushing (having replaced it previously) which has held up well, not having gotten oil-soaked over the years. However, I too would be inclined to replace an original bushing at this point given the age and intended useage, and increased interior noise is the only downside. Do consider having the trailing arm tab welds reinforced - the car's well engineered to handle stresses, but when you beef up the bushings, stress that was previously absorbed by the bushing is now being passed through to a metal part originally designed for different stress factors.

    Hardly anyone mentions the motor mounts these days, but keep in mind the stock motor mounts will eventually stress crack under driving school conditions. In the earlier E30's like yours (& mine) this means the motor will shift left when cornering through a right-hand turn, and the power-steering pump pulley will cut through the lower radiator cooling hose, dumping coolant (or water, depending what you're running) mid-turn, and throwing you into a big spin, plus making a big mess.

    I have Vorshlag motor mounts - very nice, they work well.

    http://www.vorshlag.com/product_inf...id=99&osCsid=78c87529ffd3b0afd7861f7dca5b767c

    Consider upgrading your rear transmission mounts as well (since you have the driveshaft out), although those aren't impossible to access.

    There are a lot of short-shift kits out there - I have: http://www.autosolutions.net/

    Unless you're pulling a transmission, your access for that is the most with the driveshaft out, and pulling the motor mounts. Short-shift kits are definitely worth it, a huge improvement over the inevitable slop in the original after many years/miles (in case you didn't do that already).

    02m3smg2b guest

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    additional upgrades

    I took care of most of what you mentioned, motor mounts are now the TMS with the aluminum cups, all the TMS reinforecments, sway bar link, front sub frame, and will do the trailing arm reinforcement and welding while I am working on the trailing arms. (I am doing the trailing arm bushings)
    I did the ucc evo 3 short shift..but there are a few additional components around there I'll have to save for when I have to do a clutch replacement. (I could not get that stinkin pin on the shift coupler out from below)

    I had already done the xmission mounts but I think I just went with stock there. It woud not take much encouragement to get me to go ahead and upgrade them though..as they are once again off the car.
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    MGarrison

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    Part #3?

    [IMG]

    If it's #3, ya, that's a nuisance, but not impossible. I think I found jamming an inspection mirror up there to be helpful to eyeball things, but I forget what I used to unsnap the clip - took a bunch of tries though!

    When you get around to the clutch, the top-most transmission bolt is a _real_ hassle to access. You can see it from topside behind the head with the motor mounts off (to lower the transmission for additional clearance) but it's too far back to get anything on it where you'd have leverage to turn it. Ugh. And there's not much access to eyeball it at all by using extensions longer than the transmission itself to get to the torx bolt. If you can get someone to help guide the socket onto the bolt from topside while you're underneath, it'll save a lot of time from hunting blind until you manage to get the socket on the bolt. Thankfully you won't have to worry about that until clutch time! Good luck w/ the project!
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    Brian A

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    On my 1987 325ic, I struggled for an hour trying to remove the dreaded clip. Ultimately had to put a jack under the transmission, unbolt the rear transmission mount and lower it down a couple of inches to get clearance on the top of the transmission.

    My 1991 318i by contrast LOST the clip at 80 mph on Thunderhill. Shifter went all noodly, let out the clutch slowly and discovered the transmission had put itself in 1st gear. Fortunately, I heard the rapidly rising revs and avoided the "money shift". Drove myself back to the paddock in 1st gear.(http://www.youtube.com/user/BrianAfta#p/a/u/2/Hgh9katyfP4)
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    MGarrison

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    The 'spring' part of the clip is flexible - I think I bent mine a little getting it off and re-bent it to make sure it would snap back in place securely. Ya, losing the clip altogether is not what you want - eek!

    02m3smg2b guest

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    actually #17

    i got past #3, try try pry pry...i was planning on replacing part #13, and the seal, where the shifterbgoesninto the tranny....along with #19 in the diagram, i could not get the pin, ...#17 out.

    02m3smg2b guest

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    trailing arm removal

    If I am replacing the trailing arm bushings do i really need to Loosen the drive axle nut? most post and bently seem to indicate to remove the drive axles at both the diff and the wheel hub, Is there really any need to remove the axle at the hub? why not drop the trailing arms with the outer axle and components attached?

    thanks!!
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    granthr

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    If I understand your question, you can drop the whole subframe including diff (final drive) with the half shafts still attached to the diff. Drive shaft will have to be disconnected from the diff. Now just be careful NOT to extend the suspension out of it's normal range of motion b/c you can damage the halfshaft cv joints.
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    panmarcum

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    For that #3 part I found a link that used a radiator hose pick from harbor freight but sorry I cant find the link now

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