Drive shaft center bearing

[Doyt W. Echelberger]

Hello Dennis.............When my center bearing failed, it squealed and 
shrieked, metal on metal, under load. I could put it in first and 
accelerate and the shriek got really loud. The drive shaft was turning and 
the bearing wasn't. The faster the shaft turned, the louder the sound. 
Yours is just the reverse, regarding the things that make it happen.

"Rumbling and vibration"  sound more to me like heavier masses being 
involved. Or better yet, an exhaust pipe rubbing against a turning drive 
shaft. When you let up on the accelerator, the motor mounts and tranny 
mounts allow the engine to change position on its longitudinal axis, and 
the exhaust pipe moves like a lever in this situation, and may be twisting 
over and touching the drive shaft at some point.

There isn't much pressure on that center driveshaft bearing, and the mass 
of the bearing itself is insignificant. It is suspended in the center of a 
rubber panel, which allows it to move with some "give."  Difficult to 
imagine it rumbling.

Rumbling would imply several heavy masses bouncing along on each other. 
Like an exhaust pipe and a driveshaft.

Just my opinion, if I had to guess. Look for clearances between these two 
things, and look for evidence of contact. You may have a soft tranny mount 
that is allowing the power train to shift  beyond expected limits.    Doyt 
Echelberger  87 5ktq


 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>.
At 09:27 AM 10/12/2001 -0400, you wrote:
>What is the symptom of a center bearing going south?
>I have a vibration/rumbling on slight deceleration. Not under load, and 
>not when coasting with the clutch in, and not at +50mph. Does that sound 
>like a center bearing, or carrier?
>If so, which BMW unit crosses over? Please save me an hour searching the 
>archives.
>
>Dennis
>Denver