Clutch rattle and Thunk--Advice needed

[ron c]

My '04 1150RT with 29k miles developed a clutch rattle. In neutral, at idle, clutch lever out, there is a noisy rattle from (I suspect) the clutch. Pull in the lever the noise goes away, release the lever the noise returns. It started softly 5k ago and has gotten worse since then. The rattle is now noticable in gear with the clutch pulled in. It has become very annoying. The clutch engages/disengages smoothly and there is no slippage. When pulling away from a stop there is a loud clunk from the same area. The dealer says it is normal and half of the bikes do the same thing. I have escalated to BMWNA customer service. They said they will review my case but stand behind their service technicians. I don't expect help from BMW. Can this possibly be typical? Have others had this symptom? What are my options? All help is appreciated.

 

Regards, Ron

Round Rock, Texas

[Ken H.]

Well it is typical at least to some extent. It's really more of a tranny gear "rattle" than a clutch one if it's the noise most of us are familiar with.

[SWB]

Search the archives here. I've seen several posts with guys claiming that they solved their "tranny rattling" problems with a different transmission oil (synthetic, or of a different viscosity).

[bmweerman]

I just changed the tranny and final drive fluid and put in Mobile 1 synthetic gear oil....

 

 

Sweet!!!

 

Pretty much solved that problem for me.

 

Good Luck!!!

 

Cameron

[ShovelStrokeEd]

About 2 more pounds of flywheel weight will cure it.

 

The alternating power pulses so far apart at idle are causing the meshing gears at the input shaft and the intermediate shaft of the transmission to bang back and forth on their gear faces from drive side to coast side. It greatly contributes to pride of ownership to be sitting at a light next to a HD and have your bike sound like a tin garbage can with 4 rocks in it rolling down a hill. The good news is the HD rider probably can't hear it.

[ron c]

Ok, I'll try different oil in the xmission. That seems to have quieted the rattle for some. What about the clunk upon engagement?

 

Ron

[Berts]

It greatly contributes to pride of ownership to be sitting at a light next to a HD and have your bike sound like a tin garbage can with 4 rocks in it rolling down a hill. The good news is the HD rider probably can't hear it.

 

Now THAT's funny!

[flatbutt]

Ok, I'll try different oil in the xmission. That seems to have quieted the rattle for some. What about the clunk upon engagement?

 

Ron

 

Just a guess . . .perhaps you are engaging too quickly? Is this your first beemer? These clutches are a bit different.

[Cali Kid]

I hate to say something that may overly concern you, but the way you described the noise is exactly the way I would have describe mine, up until I pulled the tranny for a spline lube at 36K. There I found that the splines were worn and the disk 98% worn. Not sayin that's the case, but it sure sounds familiar. Same noise, same progression, same mileage, same "they all do that BS".

Let me know if you do get them to tear it apart, I'd be curious.

[Ken H.]

What about the clunk upon engagement?

TADT

[ron c]

Flatbutt, I'm not sure what you mean by "engaging too quickly". If you mean a rocket start as in dumping the clutch the answer is no. I don't do that. If you mean engaging at too low an rpm the answer is still no. It is difficult to do that amyway without stalling because first gear is so tall. The clunk is there with a smooth easy acceleration from a stop. I can make the clunk worse with a rapid take off.

 

Ken H: What does "TADT" mean.

 

Thanks, Ron

[Eckhard Grohe]

TADT

They All Do That

[ShovelStrokeEd]

Wait a minute.

They don't all do that.

A clunk when you engage first gear, as in shift from neutral to first at a stop, is normal and indeed, TADT.

A clunk while engaging the clutch and the bike is starting to move is not by any means normal and should be looked at. Possible places range from transmission input shaft bearing (very expensive) to drive shaft rubber isolator (cheap) with a bad throwout bearing or pushrod somewhere in between.

[ron c]

Well, BMWNA contends my noises are normal and are not offering any warranty help. Most on this list agree the

clutch rattle is typical. There is disagreement on the

list about my clunk when engaging the clutch. With no help

from the dealer or BMW I guess I'll just ride it until the

clunk becomes an explosion. What a disappointment that a world class bike is saddled with a third world transmission.

Regards, Ron

[ShovelStrokeEd]

Does the clunk go away if you take up the slack on the clutch cable first? It might just be drive line lash which is plentiful on the boxer bikes.

[ron c]

Does the clunk go away if you take up the slack on the clutch cable first? It might just be drive line lash which is plentiful on the boxer bikes.

 

The clunk can be reduced or eliminated if I let out the clutch to near the point of stalling and then feed in the throttle.

Moments after I changed oil to Mobil 1 synthetic

I got a call from my dealer saying the regional rep wants to ride my bike. This is after BMWNA told me the rattle and clunk are normal. The saga continues.

[ShovelStrokeEd]

A little drive line lash is normal. If I get sloppy I can get a clunk from the drive train while shifting.

 

That doesn't sound like what you are describing. Can you detect any whining or grinding noise, in particular in the lower gears?

 

Best to have the regional rep look at your bike. He really does have the final say in the matter anyway and, usually, these guys have a pretty good idea of what is going on.

[RFW]

My '04 1150RT with 29k miles developed a clutch rattle. In neutral, at idle, clutch lever out, there is a noisy rattle from (I suspect) the clutch. Pull in the lever the noise goes away, release the lever the noise returns.

 

Quite obviously this has nothing to do with the clutch.

 

The problem is quite clearly in your transmission, since when the clutch is pulled in, and therefore nothing in the tranny is rotating, the noise stops. Release the clutch, and the input shaft of the tranny is now rotating and ....ta da! ...you have the noise.

 

The problem is either excessive gear lash (unlikely), or else a bad bearing on the transmission input shaft (very likely).

 

Bob.

[ShovelStrokeEd]

Bob,

It may not be a bearing at all.

 

Think this through a bit.

 

Boxer motor with firing impulse every 360 degrees of crank rotation. At idle speeds of 1000 RPM or so that means 1/1000/60 or 60 milliseconds between firing pulses. With the light crankshaft and flywheel in the the 259 motor that is plenty of time for the whole assembly to decelerate a bit. Then comes a firing pulse. Bang, the stright cut gears on the input shaft and the intermediate shaft hit each other due to acceleration. Then everything slows for another 60 msec or slow causing the gears to go back to the other faces due to oil drag. Then it repeats. The sound is very much like a rattle and actually similar to the sound the cam chain makes. That it goes away when the clutch is disengaged does prove the noise is in the transmission. BMW has been chasing this problem on the oilheads since day one with, to my knowledge, 3 different modifications to eliminate it. No full success yet.

 

A bearing failure, or impending bearing failure would manifest with more of a growl than a rattle and be present while the bike is moving under power. I know, I recently went through one on my GS Adventure.

 

The rattle is really nothing to worry about, just the nature of the beast.

[RFW]

Bob,

It may not be a bearing at all.

 

Think this through a bit.

 

Boxer motor with firing impulse every 360 degrees of crank rotation. At idle speeds of 1000 RPM or so that means 1/1000/60 or 60 milliseconds between firing pulses. With the light crankshaft and flywheel in the the 259 motor that is plenty of time for the whole assembly to decelerate a bit. Then comes a firing pulse. Bang, the stright cut gears on the input shaft and the intermediate shaft hit each other due to acceleration. Then everything slows for another 60 msec or slow causing the gears to go back to the other faces due to oil drag. Then it repeats. The sound is very much like a rattle and actually similar to the sound the cam chain makes.

 

I understand this problem well since my K100 had a similar problem when cold. After tearing down the motor, it turned out to be a thrust washer that locates the gear driven by the crankshaft, which was a few thousanths of an inch too thin.

 

The first point I was trying to make in resonding to the original post was to point out that he was in error in assuming this had anything at all to do with the clutch.

 

Beyond that, I had assumed that he knew the difference between what was a "normal" rattle, and a much more serious noise, and just figured it had to be the latter and commented accordingly.

 

Anyway, your points are well taken.

 

Bob.

[ShovelStrokeEd]

Some of the K transmissions had a helical set of gears on the input and intermediate shafts that delivered a bit of end thrust. The shim pack was pretty critical on them. I don't think that design translated into the M97 and later transmissions.

[RFW]

Some of the K transmissions had a helical set of gears on the input and intermediate shafts that delivered a bit of end thrust. The shim pack was pretty critical on them. I don't think that design translated into the M97 and later transmissions.

 

Sorry, but I may not have made myself clear on that. The gears in the K100 I referred to were the ones on the end of the crankshaft, and its mate on the motor's auxiliary shaft. The driven one (on the auxilliary shaft) was the one that had a shim on its face to stop end float.

 

They are helical gears, and just as you mentioned in the transmission example, the resulting end thrust can cause the driven gear to bang around axially, if end clearance is too great. Here, as in the transmission example you cite, the shim thickness is critical. I found that BMW had installed a shim that was too thin at the factory, resulting in the noise, so I bought the correct thickness shim and installed it. It was a $3.00 part, that caused me a number of hours work tearing down the motor to put it in.

 

Anyway, my reason in mentioning all this was only that I understood the point you were making about how torque "pulses" from the motor can cause gear rattle (whether in the transmission, or in my case, in the motor).

 

Bob.

[ShovelStrokeEd]