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Re: 1990 735I knocking noise? (archive)
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Posted by alex lynch on December 16, 2001 at 10:08:49:

In Reply to: 1990 735I knocking noise? posted by Randy. on December 16, 2001 at 00:11:55:

Sounds like the centre support bearing on the driveshaft. Did you check this when you checked the u-joints? The bearing is mounted just aft of the centre u-joint and is surrounded by a rubber sleeve. Over time, the sleeve deteriorates, then tears and allows the centre of the driveshaft to move laterally. This causes the driveshaft to hit against the underside of the car resulting in the noise you have described. As the rotational speed of the driveshaft increases, the lateral movement decreases. This is why the noise appears only when you are accelerating.

Regards

Alex

Anyone have this problem? My 1990 735I drives and shifts fine until I slow down for traffic. As I begin to speed up this terrible knocking noise begins (underneath the floor board) and then goes away as I speed up. We've checked everything including the u-joints and found nothing that would indicate a problem. Seems to do it more often when I am braking or slowing down from highway speeds. Thanks for any info.. Randy.




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