Cardan Shaft Spring (broken)- Anyone have Diagram?

[barcelona_r65]

Yesterday while "cruising" down the street in 3rd gear, I heard (and felt) a "metallic CLANK!" under my seat ... I thought, in fact, that the spring had fallen off my center stand and it had hit the asphalt ... I stopped and no ... the side and center stands were in their places.

I started back up and in 1st ... ok
2nd ... ok ... but when I hit 3rd there was this HORRIBLE grinding sound and friction that actually felt like it was "braking" my bike ... I shifted back down to 2nd and it went away ... back up to 3rd ... YIKES! ... up to 4th and the same ... (almost a "grindstone" like feeling) ... so I decied to roll the few blocks to my mechanic ... he had replaced my clutch just a few months ago ..

Of course, by the time I got there, and after turning the last corner, I began to upshift 3rd, 4th and 5th (without taking the RPMs up too high) and it shifted perfectly ...

My mechanic took if for a spin ... upon "dropping" it into 1st with elevated RPMs ... it "clang-ed" a bit and he cringed ... but more like a Cardan clang than what I had felt ... he rode around the blocks and came back ...

"Perhaps the spring that separates the cardan from the flywheel and maintains the correct pressure has broken ... I'm not sure, but be careful because I've seen it fly out of the rubber boot and if it hits your ankle (which is right there) it's like a knife.... Of course, you run the risk of the transmission locking up as well ... if it's the broken spring, it may have fallen back into place and could "fall out of place" tomorrow, next week or next year ... but it should be replaced.  There is also a spring in the clutch assembly that may be the problem, but since I didn't feel anything except what seems to be a "loose" cardan shaft ... I'd have to open it up to see ... Bring it in on Monday ..."

So, any and all ... what does that sound like to y'all?  Does anyone have an Exploded Diagram so I can see what he's talking about? ... I've created my own image in my head

[barcelona_r65]

could it be someting like the #4 from this diagram I found? ... I'd really like to see an overall exploded diagram of the entire drive train ... from the front to the back ... if anyone's got it ...

http://www.realoem.com/bmw/diagrams/m/d/5.png

[drewboid]

I don't see why it would make any difference if you were in 1st and 2nd or in a higher gear. the shaft and spring are powered and rotate no matter what gear you are in.
sounds more like a tranny problem - 1st and 2nd are engaged by the same shift fork.
Drain the tranny oil and look for any indication of broken/worn parts.
bummer!!!

[Bob_Roller]

I don't think I would ride the bike, until the problem is found and repaired, you may cause more unnecessary damage .

Have you checked the prices of replacement parts, the driveshaft alone is $650US .

[nhmaf]

While it *might* be the spring in the cushion drive mechanism of the driveshaft, I agree with Drew and Bob that it wouldn't matter what gear the bike is in, it would only be the spring's relative position and whether the broken ends were together or not.  And, the spring is not under the rubber boot - the rubber boot is where the  universal joint is (left end of the picture link above).     An "easy" thing that you can check is to see if you've broken off a bolt at the universal joint coupling to the transmission's output flange by loosening the clamps around that boot onthe swingarm and pulling it back to check that the (4) bolts are still firmly in place.

If it is truly a gear- specific thing, it does sound alot like a transmission issue.    Drain the transmission oil and look for metal shards.   If there are, you've found the problem.  If there aren't any, it is going to take more investigations to uncover.

[barcelona_r65]

The more I think about it, the more I believe it was something that worked it's way into some place it shouldn't have ... a screw or bolt that had fallen loose and somehow got into contact with a spinning part ... wedged into a spot where it rubbed against something else for a few up and downshifts ... until it worked itself out of the tight spot ...

Probably not the best situation ... but maybe not the worst case scenario ... right? ... I'm gonna slip the boot down tomorrow and see what I see ...

How do I ask my mechanic not to rip me off without offending him?  I trust him to some extent ... however, my ignorance of these things set me up as a perfect target ... Do I ask him to "show me the part" and then stare at it like a dummy when he says it was the "so-and-so thingy"? ....  :-/


I rode to work today and there is literally no evidence of what I experienced the other day ... in fact, if I had lent my bike to a friend, by chance, and he returned it without telling me about it ... I would think that this is the same bike in the same great shape as it was last week ...

What to do?  :-?

[Bob_Roller]

That's your call, but if it is a real problem, it may come back to 'bite' you some time in the future .

It all depends on how comfortable you are with it !

[Rob Valdez 79 R65]

Elevate the rear wheel so you can turn it.

There are four screws holding the driveshaft to the transmission.  

Pinch each one through the rubber boot to see if you can feel any that are loose, or perhaps you find only 3???

[barcelona_r65]

That sounds good ... I was "squeezing" around on the boot, but not really sure what size the bolts are or where I'd feel them exactly ... that made it tough ... I did notice, however that the boot is a bit dried and cracked ... and greasy/dirty underneath ...

Riddle me this:  Does the boot act as a flexible seal for an area that's full of tranny fluid/oil? ... or does it just work to keep rain & dirt out?  I guess what I'm asking is, is that boot part of a sealed environment that holds all the fluid/oil or is it "empty" in there ... If I attempt to "slide back" the boot to see the 4 bolts, will fluid spill out on the floor? ...  :-/

If one of those 4 bolts were to have fallen out, is it possible that it's sitting in one of the folds of the boot? ... If it's slid further down the cardan towards the rear wheel, is there anywhere that it could just be sitting there enjoying the effects of gravity while the vibrations from riding are slowly (or quickly) moving it to a more precarious position?

I ask all of this because (although I know it's not the best idea) I had to rely on it to get to work today ... and it felt as normal as ever ... (Although I know that there's something broken or out of place in there somewhere)

What'ya think about all that?

(I'd really like to see a photo of what all this stuff looks like in "real life" ... Up til now, I'm just using my imagination ... does anyone know where there might be pictures posted of the cardan, etc?)

[Bob_Roller]

The pleated rubber 'boot', keeps dirt and the like out of the universal joint, and the rest of the 'propeller' shaft (official term in the shop manual) .

There is about 150 ml of gear oil in the area between the rear drive, and the transmission, so you will get some oil when you remove a clamp and pull the boot back, but it's not full of oil .

If a bolt did come out, it could very well be sitting in there, but with a downward slant of the drive shaft housing, toward the back of the bike, it would probably work it's way towards the rear drive .

[barcelona_r65]

...
I got another good "CLANK!" today followed by a few "crunch, crunches" that led me right to the mechanic ... I got freaked and decided to leave it in his hands ...

I'll let you all know the "verdict" when it comes in ...

Thanks for your help/advice.  

[Bob_Roller]

Probably a wise move on your part .

[barcelona_r65]

 :-/

I just got a call from my mechanic.  He took her out for a spin (10 miles) and heard or felt nothing.  He said to me "All 4 bolts are in their place, you can feel them through the boot" ... "I don't know what to do if I don't have more data (like it only happens when engine is hot, only in 3rd gear, only ... etc) ... I could open it up and start looking around, but how do I charge you for that? ... understand?"

I said, "since you're going to change the oil, you can check the magnetic tranny plug too ... perhaps you'll find something like a half of a screw or some metal shards or something, right? ... that may lead us somewhere..."

"Sounds like a smart idea" ...I'll do that ... and I'll give you a call and let you know.

hmmmm ....    :-/

[Rob Valdez 79 R65]

This is why this is the best time in your life to learn to be a mechanic.

I rarely venture under my car's hood, but I am the only one to work on my bike.

Unless your mechanic is an experienced airhead BMW mechanic, he can cause more harm than good.  Like a 10 mile test ride.

What does he normally work on?  Any with shaft drive and the associated parts, like final drives?


As soon as I bought my R65 in 1980, I started collecting tools!  

[barcelona_r65]

Wow ... looks like someone just jumped to a quick conclusion and passed a [mis]judgement ...    

My mechanic Carlos (who has been my mechanic for 11 years) of Style Moto (calle Berlin, nº 89 is one of the few specialized independent shops in Barcelona that deals exclusively in BMW's ...ok ... he works on Honda Skooters too, but that's because Barcelona is "buzzing" with them, they're like mosquitos...)  

In fact, the 10-mile ride is pretty logical when he needs to explain to his team (his brother and 5 other certified BMW mechanics) what they're looking for ... that makes all the sense in the world when you need to get a job done and get it done right ... Imagine if Carlos just had to tell them "this guy says he heard a CLANK then a tic tick crunch ... fix it, keep track of your hours, then we'll bill him"  ... C'mon Rob, that wouldn't be a very efficient way of getting the job done.

Being that he's the "master mechanic" he wants to be able to pinpoint the problem before advising and instructing his team, hence the ride around the block that, when he heard nothing, he decided to give it more time ... maybe to see if it was related to the engine running hotter ... or something like that.  His ride led to a 10-mile total where he finally "gave up" after hearing/noting nothing out of the ordinary ...

I wish I had the time and money to learn all about my bike's mechanics. I'd love to be able to take it apart from head to toe like I did with my 1970 Chevelle Malibu Convertible ... "back in the day" ... I almost would prefer to be so "loaded with moolah" that I could tell Carlos just to take it apart and start searching and not to worry about his time, that I'd take good care of him...  The bummer is, I don't have the time, money nor the space to take this on at this stage in my life ... maybe in the future, I hope.

   So that's my story and I'm stickin' to it!