Centre Bearing Carrier

decoupe

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It would appear that my centre bearing carrier on the driveshaft has been installed backwards which may be linked to mild vibration - noticeable at low speeds when both in gear and out of gear.

http://i54.photobucket.com/albums/g120/decoupe/IMG_1256_zpstkw5gtzt.jpg

The manual clearly shows the open face of the carrier should face the front. The manual says to remove the circle and dust cap and press the bearing out. The bearing itself is fine. A new unit with the bearing is pretty cheap but I still have to get it off the driveshaft.

How exactly do you support the bearing in order to press the splined shaft through without damaging the driveshaft and trashing the unit?

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bert35csi

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Yeah, the center bearing is installed backwards. The rubber surround on bearing should be facing the spline shaft. Probably the easiest way to remove the CB is to cut off the rubber surround, remove outer metal shell and then use a bearing puller/separator of appropriate size (kits can be bought cheap) to remove the remaining bearing from drive shaft. Don't forget to get new BMW front/rear dust caps as they are cheap enough.

The CB in these 2 pics is from my E24 M6 install, but should the same install procedures as on the E9 coupes.
P1040051.jpg


P1040052.jpg


E9 workshop manual installation pics.

More detailed CB install instruction/pics in the E24 workshop manual here.
 

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Stevehose

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I modified a cheapo Harbor Freight puller for this, works great.

IMG-20130831-00070.jpg


You'll need to grind the ends down to fit all the way on the the bearing from this:

IMG-20130831-00069.jpg


To this:

IMG-20130831-00068.jpg


Note the bottom is trimmed off and the leading edge has more of a "tab" on it..

Bearing comes right off then I use a 1' long pipe the same diameter as the bearing to pound the new one on.
 

lloyd

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It would appear that my centre bearing carrier on the driveshaft has been installed backwards which may be linked to mild vibration - noticeable at low speeds when both in gear and out of gear.

http://i54.photobucket.com/albums/g120/decoupe/IMG_1256_zpstkw5gtzt.jpg

The manual clearly shows the open face of the carrier should face the front.


My only experience with installing the center support is as depicted in the manual. That being said, while replacing a transmission mount on an automatic E3, I seem to recall encountering a "reversed" center support similar to yours. Since there were no apparent ill-effects, the support was left undisturbed and the car was driven for quite some time without any known drive shaft issues. I have also heard anecdotal stories about two-piece "out-of-phase" drive shafts that also did not exhibit any unacceptable vibration.

I am not advocating any deviation from the recommended orientation of the center support, but bear in mind that it's primary function is to "support" the shaft, allowing the spinning mass to float while absorbing/minimizing nominal shocks, bumps and vibrations. The better the drive shaft's balance and alignment, the less critical the center support's function. As you know, the center support is typically installed with a "slight" 2mm preload in the forward direction. I haven't given this much thought but it may be that a reversed support could function better (or equally well) without that recommended preload or by possibly slight tensioning rearward.

If you have the time, it might be worthwhile to jack the car up and safely observe the drive shaft in action to rule out other possible causes, including significant imbalance, misalignment and drive shaft coupling issues.



More food for thought? Are there other available center supports that are superior to the original design/construction and easily adapted to the E9/E3?

Image of installed E36 (not E9/E3) center support bearing. Notice orientation.
pic5.jpg
 

decoupe

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Lloyd - although I can't disagree that it doesn't look like it should matter what the orientation is given the design and purpose is support, BMW consistently shows it one way (for the e9, 12, 24, 21 etc) so I ordered a new one. It won't get here in time so the old will go back in for now and it will get added to the to do list post surgery.
 

bert35csi

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The mounting holes on the CB tabs are assymetrical, therefore, it can be correctly mounted only one way. Otherwise, if mounted in reverse, the front and rear drive shaft will not be perfectly aligned, thus probably causing a fair amount of vibration.
 

decoupe

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Gold Star to Bert35csi!!!

Bert - well that explains things - went and looked and they are offset differently which would definitely create issues.

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lloyd

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The mounting holes on the CB tabs are assymetrical, therefore, it can be correctly mounted only one way. Otherwise, if mounted in reverse, the front and rear drive shaft will not be perfectly aligned, thus probably causing a fair amount of vibration.


Excellent point. The assymetry and likely misalignment escaped me despite it being in your pictures. I haven't had to replace one in some time, fortunately. :smile:

In retrospect, I wonder whether someone modified the bolt holes in the reversed E3 example I mentioned.


P1040051.jpg
 
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