Transmission clunk

[plc]

G'day All,

Well after reading on the forum about transmission clunks and mentioning briefly my noises I thought I would give the full story and ask for some advice.

Ever since I bough the bike, very occasionally I would get a clunk somewhere in the drive line, usually on the overrun and usually felt at the right foot peg.  As it was occasional no big deal. Earlier this year I put all new oils in the transmission all seemed good. Replaced the clutch not long after so all new oils again and new stretch bolts for the drive shaft to transmission coupling.

Had a slight leak near the boot and had to top up the shaft oil with about 50 mL of oil and a day after that the clunking became somewhat more regular. Very noticeable on the overrun, particularly in traffic. So when I got home I parked the bike in neutral and rotated the rear wheel. No noise. I felt the uni joint through the boot and all the bolts feel tight in place. I rocked the wheel with a finger on the uni joint to find free play in the final drive and there was a little bit more than mates R100 but not a horrible amount.

So I put the bike and gear and it makes no noise before hitting compression.  I pulled the clutch in and rotated and there it was. Noise every time I initiated a turn or rocked the rear wheel back and forward. If I steadily rotate forward there is no noise. If I rotate then stop, rotate then stop and so on, I get a noise on each take up. So I thought it must be something to do with the input shaft.

I intend to change the oil to see if there are any chunks of metal, but probably won't get to do that until next week.

I would appreciate any thoughts people may have on the matter.

Best wishes,
Paul

[plc]

Hi All,

I am guessing by the silence on this thread I have an out-of-the-ordinary fault.

May have to visit a BMW mechanic tomorrow.

Best to all,
Paul

[Bengt_Phorqs]

Paul, don't give up just yet.  You caught all of the American cousins over the long Thanksgiving holiday.  

Have you removed the rubber boot and examined the u-joint and stretch bolts?  That would probably be where I would begin.   My philosophy is do the simplest thing first.  Most likely though, as you describe the problem, it's a clutch issue and you'll probably end up pulling the tranny off once again.  That's probably what your mechanic is going to do and if you've done it once, then you know how.  It gets easier the second time around.

[Lucky_Lou]

Does it do it as you change gear or just when you decelerate ? could be another spline issue common down under at the moment.
Lou

[plc]

Seems to do it most noticeably on deceleration, but it does occur on acceleration. It also usually occurs after the transmission warms up. When cold it isn't very noticeable.

The spline looked OK earlier this year when I changed the clutch and like a good boy I lubed it upon reassembly. But maybe I was a bit harsh on it.

Paul

[nhmaf]

Like Bengt mentioned - we've been visiting family and eating lots of turkey and pie for the past 3-4 days..

One of our brothers across the pond had a bad bearing on the pinion gear in the final drive, which caused a clunk and/or growling sound.   There is also a spring loaded cush drive mechanism in the drive shaft near the final drive end which could have a broken part, such as the coil spring, that might cause something like this.   Likewise, there is also a similar spring loaded shaft with engaging lobes inside the transmission that could also be a cause of a clunking.  It is rare, but sometimes the spring or one of the "Ears" on the lobes on the shaft break.   I hope that it isn't the shaft inside the transmission.   I am thinking that it could possibly be one of these spring mechanisms, as their primary purpose is to handle the load reversal and driveline shock transmitted when the bike transitions from acceleration to deceleration.   It could possibly be another bearing inside the transmission, but I'd check the cush drive in the swing arm first, unless you are really sure that the sound is coming from within the transmission (swing arm work = much less money than opening the gearbox)...

Keep us posted!

[plc]

Hi all,

Guys, thanks for the comments. I took it to the local BMW dealer and their "classic" bike mechanic took it for a spin. Suffering from stage fright my bike failed to reveal the clunk to him. But as I described it he said it is either the cush drive in the shaft or the box. No rumbles or growling from bearings and the final drive "slop" is what he said he would expect from a bike of its age. Sadly I suspect it to be the box as I feel the clink in the right foot peg as much as hear it.

So i intend to pull off the swing arm and check out the shaft and then if needed take the gearbox in and let the dealer rebuild it. Not quite ready for that job yet. When I buy a spare gearbox I will have a go.

I hope all the US members enjoyed the turkey. I will have to wait for Christmas for that to be on the menu here.

I will keep you posted on the progress.

All the best,
Paul

[Semper Gumby]

Crikey I'm stuffed....Turkey, Stuffing, Sweet potato pie, green beans, oh and punkin pie!!!  (Save your fork ther's PIE)


Oh yeah Tranny noise!

Is it a hollow kind of "Thonk"?   Then I think it is one of the shafts is loose in the tranny and is moving forward and aft.  Needs to be re-shimmed I think.  Not normal.  Go into tranny.  Sorry.  Replace bearings while you are there and look for other damage.  Why this happens I haven't a clue.

This advise worth all of two cents US.  Not what it used to be!   :-/

Oh incase you were wondering wher punkin pies came from??  HOHO!

[plc]

Dropped all the transmission oils today.  Gearbox and final drive oil were both nice and fresh looking. Shaft oil was cloudy, obviously water got in somewhere.  

Shaft bolts were all tight so that was good. Uni joint seems all good thus far too.

Paul

[Semper Gumby]

Hi Paul,

Water gets in to the drive shaft through the rubber boot on the speedo drive cable at the tranny.  If the boot is anything less than perfect replace it.  Once you get the new one on seal the top with some heat shrink tubing or some RTV sealant.  

We have also heard of water getting in the Odo reset rubber button on the glass face of the later model speedos and then running down the entire length of the speedo cable into the drive shaft.

This is why I change these oils (tranny, shaft and final drive) every six months - to look for problems.  Too many expensive parts to be sitting in water!

Good luck,

[Rob Valdez 79 R65]

Bill, that picture is a hoot!  (I stole it quickly!)

[Semper Gumby]

Bill, that picture is a hoot!  (I stole it quickly!)

Some things were just meant to go Viral!!!   8-)

[Ed Miller]

I dunno if I like pumpkin pie any more.  

[montmil]

That's just plain 'ol sick, Bill. I love it [smiley=ROTFLMAO.gif]   Monte

[plc]

Hi All,

When I cleaned off the gearbox drain plug underneath the grey paste was a few little sharp bits of metal.  May be a sign it is the gearbox cush drive, or some other gearbox.

Paul