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    Planning a drivetrain/suspension service

    At some point in the next year or so, I’m planning to drop basically everything from the transmission back and refresh a bunch of stuff. The car has 149k miles on it right now and a lot of it is original, so I want to refresh it. Would love some feedback on what I’m planning to do. Also have some questions at the end of the post.

    I want to replace the DMF because some clunkiness, gear rattle, etc. makes me feel like the damping mechanism is wearing out. I figure that’s a good time to refresh the clutch kit, shift bushings, etc.

    The original driveshaft has been making the cowbell noise for years. Could grease the splines to take care of it, but given its age I want to just replace it.

    Every bushing and joint in the rear suspension, except for the spring perches and RSMs, is most likely original. Time for a refresh. Also, I want solid subframe bushings because I’ve read the NVH/benefit ratio is just that good.

    Given the overlaps in labor required for many of these jobs, I’m planning to get them done all at once.


    Goals:
    1. Refresh everything that ought to be refreshed
    2. Improve what I can without significant NVH penalties (this car is a DD, and there’s no aftermarket exhaust to drown out noise)
    3. Maximize the odds that, once everything’s back together, it won’t have to come apart again for several years and many tens of thousands of miles


    With all that in mind, here’s what I want to do as of now:
    1. Clutch kit (OE LuK)
    2. Flywheel (OE LuK)
    3. Clutch slave cylinder (OE FTE)
    4. Shift kit (Autosolutions – stock throw length with a longer rod)
    5. Driveshaft (rebuilt OE or aftermarket OE replacement)
    6. Giubo
    7. Driveshaft end bushing
    8. Transmission output shaft seal (current one is weeping slightly)
    9. Refinished rear subframe (thinking of buying a used one and having it powdercoated or something)
    10. Diff bushings (OE)
    11. Solid subframe mount bushings (Revshift)
    12. All rear suspension arms & bushings (OE Lemförder/TRW/BMW)
    13. Adjustable rear ARB end links (SPL)
    14. Rear ARB bushings (BMW)
    15. All necessary fasteners & gaskets for all of the above + exhaust


    Brands are largely constrained by FCP Euro's catalog for obvious reasons.


    Questions:
    1. What other potential wear items are easily replaced while in there for any of this work?
    2. What might break that I should have spares for in advance?
    3. Any advice on what kind of coating to go for on the rear subframe? And/or anyone know of a vendor that sells refinished ones?
    4. CF driveshaft: I really want one, but I think goal #3 precludes it. I’m sure most are fine, but between the sporadic issues people have had and the need to worry about heat shields near the diff flange (either bend, cut, or accept the risk of rubbing), CF seems like it’s not as sure a bet as OE in terms of being painless in the long run. Can anyone change my mind on that?
    5. Looking at new/rebuilt OE-replacement driveshafts, many (all?) seem to come with serviceable U-joints. It’s my understanding that, for parts like this, serviceability generally comes with a shorter life. Realistically, I’m never going to service the U-joint. Either it lasts long enough that I might as well replace the whole driveshaft when it dies, or it’s so short-lived that I want nothing to do with it. Anyone know of a rebuilder/manufacturer that prioritizes longevity over serviceability?
    6. Should I do the rear main seal? AFAIK, this is one thing you’re not supposed to fix if it ain’t broke, and I don’t have evidence that mine’s leaking. OTOH, 14 years and 149k miles is getting up there, so maybe it’s worth doing either way…?



    Thanks for reading this far. Looking forward to people’s thoughts.
    2008 M3 Sedan 6MT
    Slicktop, no iDrive | Öhlins by 3DM Motorsport | Autosolutions | SPL

    2012 Mazda5 6MT
    Koni Special Active, Volvo parts

    #2
    I don't know if there's enough traffic here to give you great answers, might be better over at m3post. I'm not experienced to say much about e9x yet, but maybe double check that their clutch issues aren't like ours where you don't want to use the LuK TOB, but the OE sachs or where you don't want to use the FAG pilot bearing, but OE bmw only etc...

    I don't have faith in revshift personally, so I'd make sure reviews are good on their solid subframe bushes - I was only aware they did poly really. I was very happy with the Whiteline poly bushes on my e8x subframe, but for solid I think Turner was popular?

    I wouldn't bother with CF driveshaft, seems to be problem after problem for very little gain and too much cost.

    I wouldn't go replacing everything just because of mileage. If there's no leak, keep going IMO. People create bigger headaches for themselves trying to be clever. Seen it so much with the E46 "while you're in there" b.s.
    DD: /// 2011.5 Jerez/bamboo E90 M3 · DCT · Slicktop · Instagram
    /// 2004 Silvergrey M3 · Coupe · 6spd · Slicktop · zero options
    More info: https://nam3forum.com/forums/forum/m...os-supersprint

    Comment


      #3
      Hi There - My car has more than half the miles of yours and its experiencing some play on the drive shaft when manual shifting, in auto mode you dont feel anything (DCT). I assume this is due to the age of the rubbers (early production 2008 here) and the few times that i have launched it. I found this within my google searches:

      Performance propshaft carrier upgrade keeps your driveshaft perfectly aligned, reduces drivetrain slop, and doesn't sag or wear out over time. 2-piece design doesn't require removal of the driveshaft and installs easily without any special tools.


      Just wanted to see what you guys thought of this replacement and if you think the NVH would be too much in its softest setting.

      Im planning on swapping out the guibo + center support bearing soon, can definitely feel more the play as its been hot here in SoCal.

      Best,
      Irhase46m3

      Comment


        #4
        Originally posted by Tbonem3 View Post
        I don't know if there's enough traffic here to give you great answers, might be better over at m3post. I'm not experienced to say much about e9x yet, but maybe double check that their clutch issues aren't like ours where you don't want to use the LuK TOB, but the OE sachs or where you don't want to use the FAG pilot bearing, but OE bmw only etc...
        Good call. Thanks.

        I did cross-post. Additional ideas included POR-15 and a diff rebuild. Not sure about the diff rebuild – lots of money when IDK if there's anything wrong with mine – but POR-15 or something similar seems like a good idea.


        Originally posted by Tbonem3 View Post
        I don't have faith in revshift personally, so I'd make sure reviews are good on their solid subframe bushes
        Thanks for the heads-up. Seems you're not alone in that. I kind of defaulted to them because FCP Euro carries them, but maybe the lifetime guarantee isn't all that meaningful for this part...


        Originally posted by Tbonem3 View Post
        I wouldn't bother with CF driveshaft, seems to be problem after problem for very little gain and too much cost.

        I wouldn't go replacing everything just because of mileage. If there's no leak, keep going IMO. People create bigger headaches for themselves trying to be clever. Seen it so much with the E46 "while you're in there" b.s.
        Makes sense. Thanks again.
        Last edited by IamFODI; 09-27-2022, 06:11 PM.
        2008 M3 Sedan 6MT
        Slicktop, no iDrive | Öhlins by 3DM Motorsport | Autosolutions | SPL

        2012 Mazda5 6MT
        Koni Special Active, Volvo parts

        Comment


          #5
          Updates!

          Built a huge parts list for this service. This project has ballooned in price, and not just due to creeping inflation.

          I've been tracking prices every ~5 days and ordering things when they're sufficiently below their to-date average prices. Whatever's left will likely be ordered in May. Service will take place in mid/late June.

          Added a rebuilt diff to the list. Current plan is Diffsonline, with the stock gear ratio and limited-slip unit, and no REM polishing. I don't think any of the other options is worth the price for my usage (mostly street, some track at novice level). Happy to hear arguments to the contrary.

          My rear subframe has some surface rust. It's not bad but there's a flake or two. Anyone think this might be something to worry about WRT stiffness? Should I try to source a lower-mileage one?
          Last edited by IamFODI; 01-14-2023, 07:32 AM.
          2008 M3 Sedan 6MT
          Slicktop, no iDrive | Öhlins by 3DM Motorsport | Autosolutions | SPL

          2012 Mazda5 6MT
          Koni Special Active, Volvo parts

          Comment


            #6
            I would replace the wheel bearings and clean, inspect, and repack the rear axle CVs.

            Do the rear main seal. Or at least inspect it. All rear mains leak to a certain extent. It is a single shaft seal...it will leak especially if its been in service for awhile. In the industry for hazardous liquids, shaft seals will usually have a dual seal to contain the liquid when the first seal leaks due to the likelihood of failure.

            I would powder coat the rear subframe.

            I can source a rebuilt driveshaft. I'll have the check pricing but it is usually about $600 plus a core charge. Not OEM quality but they are relatively trouble free. I've sold over 50 rebuilds for E36/46/9X cars. I am not aware of a warranty claim or issue. Other than getting slimed when trying to install it...they put an absurd amount of grease in the CV...and leaving the studs in the CV from balancing (just tap them out).

            Before rebuilding the diff...I'd check the preload to make sure the clutches aren't worn. Just jack one wheel up and turn the other wheel using the axle nut.

            If the diff has no preload or you want to spend money...I have an E9X M3 case, a ZF LSD. I just need to find a R&P shorter than a 3.62. I can build a 4 clutch ZF differential with whatever gearing that you want and I can find. I can get the REM polishing done on the R&P, bearings, races, and the spider gears - $400 extra. It's the same guy who does the polishing for all of the BMW shops. I use the racing diffs clutch pack which has worked out well for me so far.

            Comment


              #7
              Nice. Thanks, bigjae46.

              Hadn't thought of repacking the rear axle CVs. That's a good one.

              Definitely powdercoating the rear subframe. What I'm wondering is whether there's any risk that rust may have reduced the rigidity of the rear subframe. But I think that might just be me looking for an excuse to mod. 🤣

              The driveshaft is one area where I'd rather not settle for relatively trouble-free, or else I'd go CF. Do you know of anyone who does OE-quality work or better?
              2008 M3 Sedan 6MT
              Slicktop, no iDrive | Öhlins by 3DM Motorsport | Autosolutions | SPL

              2012 Mazda5 6MT
              Koni Special Active, Volvo parts

              Comment


                #8
                The I’d just replace the front bushing, center bearing and clean, inspect and repack the CV.

                Surface rust isn’t an issue. The subframe will need to be blasted before powder coating so you can inspect for any rust damage at that point.

                I haven’t looked at the subframe close enough but there might be an opportunity to gusset some corner joints to make the subframe stronger.

                Comment

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