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Old 01-03-2013, 08:46 PM   #24
latitude39
Registered User
 
Join Date: Jan 2010
Location: United States/Colorado
Posts: 136
My Ride: 2002 325xi
CSB Center Support Bearing preload confusion/clarification

Quote:
Originally Posted by grubby_baker View Post
... I did 'preload' the carrier bearing by pushing it toward the rear of the car as it shows in picture in the Bentley, even though it says in the text 'push toward the front'.
I don't think the CSB should be preloaded by pushing it to the rear.

I believe it is correct to do as the Bentley *text* states, "...by pushing the bearing forward 4-6mm from center."

I researched the reasoning for preloading. I found an explanation I liked (in the E39 section of bimmerfest): "...when the car is lowered, the Rear Differential moves upward ... and ... the Driveshaft moves forward a few mm."

The reasoning goes on to say that preloading would not be necessary at all if the CSB is bolted down when the car is resting on its wheels, as when a mechanic works from within a pit, over which the car was driven.


Bentley has confused things by showing an "xi" rear driveshaft without labeling it as "xi" (see DRIVESHAFTS 260-5 in Bentley, which the reader would assume to be a RWD).

The word "center" is confusing too. Center in relation to what?

From the Bentley photo, I am guessing that the oblong holes in the CSB mounting bracket would be "centered" if the bolts sat in the middle of those holes. However, the photo clearly shows the CSB pushed toward the "front" of the car (top of photo). The bolts are clearly off-center in the oblong holes.

The reasoning makes sense to me so I wanted to share it here.

OP: Sorry for this late information. I just found it today--I'm going to pull my own drive shaft very soon (for flex disc, csb, etc) and wanted to get my ducks in a row. I've gone cross-eyed with all the reading and sorting truth from fiction but I've think I've got it now.

Images are from realoem 1) 325i driveshaft, 2) 325xi driveshaft
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Name:	Driveshaft for AWD xi from realoem.png
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