Announcement

Collapse
No announcement yet.

Loose LTW flywheel bolts

Collapse
X
Collapse
 
  • Page of 1
  • Filter
  • Time
  • Show
Clear All
new posts
Previous template Next
    #1

    Loose LTW flywheel bolts

    My transmission started making some funky noises a couple weeks ago. I had posted a thread here asking about it. It's not a DD car so I had it towed home and pulled the trans. I only drive it on weekends and do not track or abuse it so I was surprised to find that the flywheel bolts had loosened up a little. Enough to cause the flywheel to "chirp" against the clutch and scratch up the surface where it mates to the crankshaft. I had installed a BavAuto aluminum flywheel package when I did the swap (about 1000 miles ago). After doing a little research, I've found that this is not an uncommon problem. I wish I had found out about this before I purchased it.

    Yes, I am sure I correctly torqued AND locktited the bolts.

    I'm not real keen on re-installing this flywheel. I'm probably going to sell the whole thing and buy a stock dual-mass.

    If this has happened to you, I'd like to hear about it. Did you tighten up the bolts and keep going? Has the problem re-occurred?

    Discuss please?

    TIA
    Tags: None
    #2
    did you use new bolts? (no offense or anything)
    Build thread

    Bimmerlabs

    Comment

      #3
      Originally posted by nando View Post
      did you use new bolts? (no offense or anything)
      Absolutely. They came with the kit.

      Comment

        #4
        why not buy a stock single mass and lighten it some
        Your signature picture has been removed since it contained the Photobucket "upgrade your account" image.

        Originally posted by TimKninja
        Im more afraid of this thread turning into one of those classic R3v moments, where Pizza gets delivered.

        Comment

          #5
          So are the flywheel bolts one time use lke head bolts? I just had my flywheel lightened and am about to install it. Do I need new bolts??
          Originally posted by Nicademus
          My car beats off to that car. :bow:

          Comment

            #6
            Originally posted by nando View Post
            did you use new bolts? (no offense or anything)
            This is making me think about it. I am about to put me LTW flyweel on. Do I need them??
            Originally posted by Nicademus
            My car beats off to that car. :bow:

            Comment

              #7
              Almost sounds like thermal expansion is stretching the bolts to the yield point. I'd be tempted to try stock bolts. It would be desirable to find some that had a higher tensile strength and under-torque them to keep the elasticity as the flywheel warms up.

              Differential thermal expansion is the reason for torque-to-yield head bolts, and they are why iron block/aluminum head motors can keep a head gasket.
              sigpic

              Mike

              '91 325i track car. Mostly...

              Comment

                #8
                couple of questions.. are the bolts that came with the flywheel the same as stock or different? if different, how so? grade/length/style/etc

                is the region on the flywheel thats clamped by the bolts aluminum?

                how do the torque specs provided with the kit compare to stock?

                ***

                this is just a thought. basically, for a given geometry/materials/etc of a joint, the torque spec is meant to control the joint's preload. change any of those things and you will inevitably change the preload. my theory is that in changing the flywheel from iron to alum, the stiffnes of the joint was altered. assuming the same bolt, if the torque spec was not adjusted, you wouldnt get the same amount of preload in the joint

                i imagine bmw chose the stock torque spec for the flywheel bolts in order to achieve a preload that prevents loosening under the vibrations/thermal loading of the engine. its possible youre not achieving that minimum amount of preload. even if this were true, just torqueing the bolts more might not solve the problem. no idea what kind of stress the bolts are seeing and whether or not they are plastically deforming


                this is a complicated issue, there are many things that could contribute to the loosening. other questions (rhetorical):

                -do you trust your torque wrench/when was it last calibrated, if ever?
                -did you use the stock shim that goes between the bolts and the flywheel and serves to spread the load over a larger area?
                -how clean were the threads, both on the bolt and in the crank?
                -did you have the clutch/flywheel assembly balanced?

                Comment

                  #9
                  Originally posted by chris4891 View Post
                  is the region on the flywheel thats clamped by the bolts aluminum?
                  If it is, you need to use the steel torque plate that came off with the stock flywheel. Instead of washers, the 8 bolts use this plate to evenly distribute the torque. It also acts as a spacer so that the bolt length is correct. My light aluminum flywheels havent come with this plate, so it's probably something that is easy to overlook.

                  Doesnt sound like a flywheel problem though. You can re-use stock bolts (even though I never do) with fresh loc-tite.

                  Comment

                  Previous template Next
                  Working...
                  X