Something has been rumbling for over a year. i've gone through the front wheel bearings. I noticed that it had harmonic tendencies--came up more at different speeds. Was just like my experiences of fifty years of u-joint and bent driveshaft stuff.

Sooo--I replaced the rubber center bearing hangar--the bearing was smoothe as silk. (I did tighten the compression collar on the splined part. )The vibes seem worse. Could it be the rubber end mounts going? What is typical. I'm getting tired of driving a MB 300CD that feels like an old Ford.

BTW, I did match-mark the driveline mounts and the splined connection so I know I remounted correctly.

I had my driveshaft rebuilt or rebalanced one of the two. It didn't cost that much at all though.

Replaced the driveshaft support (rubber/plastic part), the bearings, flex discs, etc.

It helps. However I can still feel a slight vibration but I think it's just me nitpicking.

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2008 BMW 335i Coupe

I'll try new flex discs next.

Is the vibration at wheel speed or driveshaft speed. The driveshaft turns over three times as fast, so the frequency is pretty high if the driveshaft is the source.

If you have the facility to set up the car to do this safely, you can run the car while the rear wheels are off the ground to about 45 MPH and slowly move a piece of chalk or crayon toward the spinning driveshaft at the front, center and rear. If the driveshaft is vibrating, you will make a mark on one side rather than all the way around.

Please don't try this unless you have the equipment to do it safely.

Good luck,

Yeah, I thought of that too, Larry. I hesitated in getting under whilst the wheels were going so fast. The vibes are certainly faster than anything associated with wheels or axels. (I had recently replaced the axel units also.) I'll jack her up again and support with substantial stands, block the front (which would probably be silly to expect security at 45MPH--- maybe chain her up to a big tree ), i'm thinking that the renewal of the center bearing support may have changed the angle of the shafts ever so slightly and affected the discs some.

The extra amplitude at about twenty under acceleration might suggest load-dependant factors since it doesn't do it to as great a degree if under a slight load. The only parts that would be stressed so would be the u-joint and the flex discs. I hardly think that the splined coupling is out of whack although if loose, it could be a definate suspect. Something is giving me fits under there and it gets my attention everytime I drive it.

Is there an anticipated lifespan on the flexdiscs? This is a 1980 w appx 200M miles.

I appreciate the input.