Driveshaft Centralizer

[RohJay]

What exactly is the function of the Driveshaft Centralizer ?

http://www.bmwmobiletradition-onlin...el=3452&mospid=47807&btnr=26_0159&hg=26&fg=10

I ve just pulled apart the driveshaft to find all components 1 to 7 are missing in mine.
And having driven it less than a couple of miles since purchase i have no idea if its absence was felt or not.

Is anyone running without this assembly?

If it is deemed essential I would like to replace all the components.
it appears all other than CAP - 26113648115, are available.
Is there alternative to this?

Thanks in advance

 

[Bertocchi]

My belief is that this piece is essential and should the item fail it will quickly beat your floor pans and tunnel to death and possibly cause injury to the occupants of the car.
I further hypothasize that by have a "split" drive shaft the load on the transmission tail shaft bearings and seals is greatly reduced by insuring the first section is kept aligned with transmission output shaft.
That being said it is necessary to support the junction of the two driveshaft halves, hence the center bearing. Many cars and trucks use this design.
Good luck with the repair and post any other questions you might have about the repair. CSL? You are very fortunate.

David

 

['69 2800cs]

I just pulled my giubo and it came out in 6 pieces!

There were no remaining connections in the rubber, so without that centering device I would have experienced the mayhem David describes. (One chunk did hit the tunnel hard as I nursed the car home with a bad vibration.)

If I can ask a question as well...I didn't find 11 or 12 on my car, and I don't see them listed on that site.

My car is a '69, and the diagram shows a 4/71 start date, so perhaps I don't need them, then again I have a 5 speed swap...sheesh it's never easy!

 

[JhwShark]

A couple of points:
The whole assembly reference called Driveshaft Centeralizer has some key critical compenents:
The diagram calls a Ujoint what is commonly called a guibo coupling must be in good shape no craks tears...
The un-numbered center bearing must also be in good condition.

As for the items in the kit#1 provide some tension along the shaft against the transmission output by way of the compression spring; it absorbs foraward/backward thrust.

As for performance and risk of not have the bump assembly (#1 kit parts 2-8), I am not sure...you do or do not have the compression spring (#7)?

There could be a risk of forward thrust against the tranny that could be harmful...we need someone else to comment on the risk and criticality of this kit. Of course if it is in the design it is probably important.
Jon

 

[jranmann]

A point of possible interest is the driveshaft's overall balance in relation to the 'centered' line of torque thrust. My interpretation is that the driveshaft itself can be balanced to offset and compensate for this on a remote spinup unit (not unlike balancing one's tires on the wheel) but the bench set up makes the assumption that the center point is a constant...

...which means that if the assembly you mention is not present or if it's even loose the center will drift back and forth, according to torque direction, load and road condition making a smoothly balanced shaft impossible consequently wearing the guibo and joints until they crack under stress they were not designed to take...only then will the driver begin to feel the vibration of the shaft itself...ususally on power takeup but also during constant speed as the associated harmonics are crossed physically, back and forth, over the roadspeed harmonics associated with the driven wheels themselves.

 

[JhwShark]

Ran & Mercury man, Good stuff.

 

[MMercury]

If I understand the post, Rojay is referring to the small items that fit within the drive shaft and not the center support or center support bearing. For all practical concerns, these "centralizing" pieces are hidden beneath a press-fit sealing cap. To access these parts, you have to pry off the cap. In other words, you may not notice them if you merely replace the giubo.

I have no idea how critical these items are. I have seen a drive shaft without the parts, but as the giubo and center support bearing were both shot, it would be guessing to say the centering parts played any role in the failure of these other parts. The linked diagram seems to make these "centralizing" parts as integral to the design of the drive shaft. Whether this is separate from the function of the giubo or rag joint is not entirely clear to me.

As borne out by the following examples, the giubo seems capable of aligning or centralize things by its lonesome.

It may be that, the "centralizer" parts, as the name suggests, only fine tunes things or keeps an out of shape, unbalanced or wandering flex disk in check - for the long term. Perhaps with the stoutest of flex joints, the "centralizers" are unnecessary. Parenthetically, one could argue that the effect is minor because these centralizing parts are easy to overlook and therefore probably go without maintenance as with many of the components, e.g., staked u-joints. More often than not, maintenance probably consists of an inadvertent wipe with a grease-covered finger. Conversely, as with the case of the staked u-joints or crankshaft pilot bearings, the centralizing parts only become necessary when other components throw off the balance or alignment. At the same time, this is probably the only reason they wear. This is akin to asking whether the chicken or the egg comes first.


To 69-2800: I am guessing that you do not see parts 11 or 12 because they do not originally belong on your particular car. Those parts look like washers and spacers that might be used to adapt the thinner ‟jurid” or reinforced flex disks fitted to automatics and some newer models. Notice the legend: "Items pictured but not listed are not installed on your vehicle or listed on another diagram."

hth

Warning: objects in the mirror may be stranger than they appear:

 

[JhwShark]

If I understand the post, Rojay is referring to the small items that fit within the drive shaft and not the center support or center support bearing. For all practical concerns, they are hidden beneath a press-fit sealing cap. To access these parts, you have to pry off the cap. In other words, you may not notice them if you merely replace the giubo.

I have no idea how essential these items are.

hth

Good point

 

[jranmann]

More often than not, maintenance probably consists of a grease-covered finger.

Not to put too fine a point on this but after my divorce, routing about in my basement closet I came upon of all things my ex-wife's 'instructional manual' and noted that she too required the same maintenance item noted above...boy, if I knew then what i realize now, things would have taken a very different track!

:mrgreen:

 

[nashvillecat]

A little dab 'll do ya?

Not to put too fine a point on this but after my divorce, routing about in my basement closet I came upon of all things my ex-wife's 'instructional manual' and noted that she too required the same maintenance item noted above...boy, if I knew then what i realize now, things would have taken a very different track!

:mrgreen:

You seem to be suggesting that, in retrospect, you would have used moly lube and preloaded the ex's center support [bearing] by no more that the recommended 2mm.

The post conjured another vision: that of lead mechanic, Ian Anderson, vocalizing about greasy fingers and his costume.

Whatever the vision, to those celebrating, happy thanksgiving.

 

[jranmann]

You seem to be suggesting that, in retrospect, you would have used moly lube and preloaded the ex's center support [bearing] by no more that the recommended 2mm.

The post conjured another vision: that of lead mechanic, Ian Anderson, vocalizing about greasy fingers and his costume.

Whatever the vision, to those celebrating, happy thanksgiving.

That's affirmative!
:mrgreen: