Transmission Problem or Just clutch?

[bornfrustrated]

So it finally happened. I've finally run into a major problem with my bike. It's a 93 k75 and I was coming home from some camping. I lost power and heard a grinding/squealing noise while I pulled over. It'll start up and is fine in neutral with the clutch out. Once I pull the clutch lever in the squealing noise starts until I let it out. If I put it in gear, it'll give the grinding noise and register that it's in gear. I didn't try to move it once I pulled over and it won't come out of 1st until I turn the bike off.

It's shifted weird sometimes since I bought it 5 years ago. Sometimes it won't go in gear all the way or it'll come out of gear but this could be because of user error. I'm at 47k miles and spline lube was done around 30k. It's always had this clacking with the clutch out in neutral too. I haven't taken anything apart yet.

My question is does this sound like an internal transmission problem, Input shaft, or a clutch problem?

[The Mighty Gryphon]

Is there any free play in the shift lever?  A lot of free play indicates a loose grub screw in the transmission.  It can cause a lot of problems with the insides of the transmission.

[daveson]

If it squeals in neutral with the lever in, that might point to the clutch. Maybe the pressure plate or bearing.

[Laitch]

. . . I was coming home from some camping. I lost power and heard a grinding/squealing noise while I pulled over.

By "losing power" do you mean the engine lost power, or the engine revs stayed the same but forward momentum slowed?

[bornfrustrated]

Is there any free play in the shift lever?  A lot of free play indicates a loose grub screw in the transmission.  It can cause a lot of problems with the insides of the transmission.

I adjusted clutch Freeplay earlier this year to be in normal spec. Engagement is later than i like but I've found that to be true for literally everything manual I've owned.

If it squeals in neutral with the lever in, that might point to the clutch. Maybe the pressure plate or bearing.

This is what I was thinking. I don't know what the condition of the input shaft splines are since I didn't have them lubed but I have paperwork from the p/o.

By "losing power" do you mean the engine lost power, or the engine revs stayed the same but forward momentum slowed?

Engine stayed running, but there was no power to the wheel. Also when I start it, there are no abnormal sounds until I pull the clutch in or shift into first. I did not try to move it in gear or shift into second after pulling over.

Also, it rolls fine in neutral. I was able to roll it into the van to get it home.

Thanks everyone. I very much appreciate the brainstorming before taking it all apart.

[The Mighty Gryphon]

I was referring to free play in the gear shift lever.  Excessive free play there can result in gears being partially engaged causing all sorts of havoc inside the transmission.  There should be some resistance to any movement in the gear shift lever throughout it's travel.  If it flops around, the grub screw is loosening and trouble awaits.

[Laitch]

Engagement is later than i like but I've found that to be true for literally everything manual I've owned.
Engine stayed running, but there was no power to the wheel. Also when I start it, there are no abnormal sounds until I pull the clutch in or shift into first.

Late clutch engagement that can't be improved by adjustment could mean the clutch disc is worn out. These discs are usually durable, functioning for 80K-100K miles or more depending on the riding styles of the users.

Difficulty downshifting can indicate lack of spline lube. Chronic lack of transmission input shaft spline lube contributes to wear of the clutch hub splines and/or transmission input shaft splines. When the teeth of a driveline splined shaft or socket are completely worn, power to the rear drive stops and is often accompanied by a grinding noise when in gear.

A YouTube video of the noise as shifting is accomplished while the moto is on the center stand might help us identify it. At the minimum, disassembly to inspect the rear drive and driveshaft splines, followed by removal of the transmission to inspect the clutch disc thickness, clutch hub splines and transmission input shaft splines is what I would undertake, based on your description.

Does the noise sound like this and are the circumstances that produce the noise the same?

[bornfrustrated]

Does the noise sound like this and are the circumstances that produce the noise the same?

That's pretty close to what it sounds like and under the same conditions. Great video by the way for what I was describing. I guess I'll pull the rear shaft and the transmission this weekend to see what those splines look like. Clutch spline lube I've read is good for about 40k? At least that's what I've heard for '90+ bricks.

I was referring to free play in the gear shift lever.

No freeplay in the gear shift lever. Also, downshifting isn't usually an issue unless I've stopped and I'm going into first. I've usually chalked this up to manual transmission stuff just being slightly out of alignment and a quick/short engage/disengage of the clutch lever remedies any difficulty.

Also I don't know if this is part of it or a separate issue, but upshifting is where I usually saw more difficulty. Sometimes it won't go all the way in gear and I need to "re-upshift" for the gear to engage.

[Laitch]

. . . upshifting is where I usually saw more difficulty. Sometimes it won't go all the way in gear and I need to "re-upshift" for the gear to engage.

Your description squares with a worn out clutch disc and/or worn clutch cable. It depends partially on whether the moto has been regularly given a competent by-the-BMW-book clutch adjustment. Inspecting the clutch pack would be helpful, after you locate the source of the screaming first.

A transmission input shaft spline lube can be good for 40K miles—perhaps longer—if was done on a cleaned splines with the appropriate paste and technique.

Keep us posted.

[daveson]

 I had problems upshifting gears when I got a brick, partly cause I rode mostly Japanese bikes, and mostly cruisers, where you tend to change gears at low revs. At higher revs and a few other changes, before long it will be a thing of the past with difficult changes.

If engagement is too late on everything manual you've owned, that sounds like a symptom of being born frustrated. Bike riding could be one of the cures.

[bornfrustrated]

Got it all apart today. Output shaft, drive shaft, and final drive splines all look great. The rear drive seal leaks a bit, but it doesn't drip. Some pictures are after I wiped excess lube off.

[bornfrustrated]

Input shaft and clutch were not so good...

Clutch had about 14k miles on it. Looks like when they changed the clutch they didn't lube the input shaft. The clutch splines are smoother than a koalas brain. The input shaft is super chewed up.
 
IMG_20211023_164922.jpg (28.91 kB . 259x576 - viewed 845 times)

So I'm looking at a clutch kit and a used transmission. My next question though. Is there anyone that makes a better input shaft that can be swapped in? Spending the money on a new transmission with an input shaft that will eventually do the same thing seems sillier than spending the same amount of money on a beefier shaft.

[The Mighty Gryphon]

Wow! that's the worst looking clutch I've ever seen.  That damage is pretty alarming for only 14,000 miles.  The input shaft wear is also unusual.  I suspect that there is something about the alignment of the engine to the transmission that is encouraging the wear.  I think there was a service bulletin about alignment that may shed some light on your problem, maybe someone has a link to it.

There should be two dowels in the intermediate section that align the transmission to the engine, one on either side of the housing.  Do you have them on your bike?

As far as the input splines on the transmission, you shouldn't need anything special to get a couple hundred thousand miles out of them.  There are lots of bikes out there with well over 100k on them that have good splines.  Just keep them lubed with a good spline lube.

[Laitch]

Is there anyone that makes a better input shaft that can be swapped in?

Not to my knowledge. Longevity is dependent upon timely maintenance with correct paste and application technique, and the owner's riding style.

The universal joint splines and transmission output shaft splines don't wear because they are clipped together and not subject to fretting—wear caused by the sliding of the splines against each other within sockets or hubs. Measure the clutch disc with a micrometer at a few points around its surface and tell us what you get.

Attached is the bulletin about alignment dowels to which Gryphon refers.

[frankenduck]

Were you getting false neutrals downshifting, like 4>3 or 3>2 when coming into turns? This is a common symptom of dry splines and if left unaddressed will strip the clutch splines eventually.

You do not need to replace the whole clutch assembly, just the clutch plate.

Hard to tell from your pic how worn or not worn the rear drive shaft splines are. Wipe off the lube and look for "the mountain effect" to assess the condition of those splines. The drive shaft splines are softer than the final drive input splines and wear faster.

More about splines here:
http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/splientology/Splientology.pdf

[Laitch]

Wipe off the lube and look for "the mountain effect" to assess the condition of those splines.

That's also known a "sawtooth profile". Instead of the splines having straight sides and flattened tops, one side gets hooked like a saw tooth and the tips start becoming pointed, like in the attached photo. Finally, the spline tops break off, forward power ends, and the howling begins. 

[bornfrustrated]

Wow! that's the worst looking clutch I've ever seen.  That damage is pretty alarming for only 14,000 miles.  The input shaft wear is also unusual.  I suspect that there is something about the alignment of the engine to the transmission that is encouraging the wear.  I think there was a service bulletin about alignment that may shed some light on your problem, maybe someone has a link to it.

There should be two dowels in the intermediate section that align the transmission to the engine, one on either side of the housing.  Do you have them on your bike?

I've never done a bike clutch, but yeah any car clutches I've done have never looked that bad. Those alignment dowels between the gearbox and bell housing are there. I saw something about them while I was trying to figure out what happened and I knew to look for them. I didn't remove the bell housing though so it's not confirmed that the dowels are in there between the engine and bell housing. I'll look next time I get the chance to do more work.

Were you getting false neutrals downshifting, like 4>3 or 3>2 when coming into turns? This is a common symptom of dry splines and if left unaddressed will strip the clutch splines eventually.

I was getting false neutrals, but it wasn't dependent on turns. I got them more often with upshifting.

Wipe off the lube and look for "the mountain effect" to assess the condition of those splines.

I did wipe off the lube on the output, drive shaft and rear. I didn't get any pictures of them cleaned off, but they all looked good.

The input shaft was definitely dry. I know it hadn't been apart since the clutch was done by the previous owner. Does the input shaft seem particularly worn for 47k?

[Laitch]

I know it hadn't been apart since the clutch was done by the previous owner. Does the input shaft seem particularly worn for 47k?

Post a photo with the same resolution and profile as the one in Post #15 and we'll have a better idea.

I believe there's a misconception about the way molybdenum/graphite spline lubes work. Only a light covering is used because the graphite or molybdenum whithin the paste bonds to metal surfaces by heat and pressure of operation; that bonding provides lubrication and protection. That's also why the surface of the splines should be clean and dry. The moly or graphite in the paste won't bond to soiled surfaces. These pastes don't work like typical grease. BMW gives the effect of the lube a typical lifespan of 40K miles on later model Bricks.

Measure the clutch plate thickness. I'm not yet convinced the clutch plate has only 14K miles on it. Was the clutch hub extending forward or rearward when it was in place in the clutch pack? Would you post a side profile of the pushrod?

[frankenduck]

Was the clutch hub extending forward or rearward when it was in place in the clutch pack?

You can see in the first picture of Reply #11 that the clutch plate is installed in the correct orientation.

ETA: And if it were installed backwards then the clutch would not work properly (if at all) because the clutch diaphragm spring would have to be compressed pretty far just to get the clutch assembly installed.

[Laitch]

You can see in the first picture of Reply #11 . . .

And if it were installed backwards then the clutch would not work properly (if at all) because the clutch diaphragm spring would have to be compressed pretty far just to get the clutch assembly installed.

If I could see that, I wouldn't have made my comment. I couldn't discern what you see but regardless, according to KC's description the clutch hasn't been working properly.

[bornfrustrated]

Measure the clutch plate thickness. I'm not yet convinced the clutch plate has only 14K miles on it. Was the clutch hub extending forward or rearward when it was in place in the clutch pack? Would you post a side profile of the pushrod?

The clutch hub extended rearward. The writing is on the transmission side. There's not really any indication it was put in backwards and it never slipped on me. I'll get a thickness measurement as soon as I can, and the video below Shows the cable operation with quite some throw.

https://1drv.ms/v/s!AjKhkI5jKmTtie9ySXV5JfPpdZmqLg

This is the next best picture I have of the input shaft though

Other pictures and the measurements of the friction disc will need to wait since it's currently at my father's place.

[bornfrustrated]

Measure the clutch plate thickness. I'm not yet convinced the clutch plate has only 14K miles on it. Was the clutch hub extending forward or rearward when it was in place in the clutch pack? Would you post a side profile of the pushrod?

The clutch hub extended rearward. The writing is on the transmission side. There's not really any indication it was put in backwards and it never slipped on me. I'll get a thickness measurement as soon as I can, and the video below Shows the cable operation with quite some throw.

https://1drv.ms/v/s!AjKhkI5jKmTtie9ySXV5JfPpdZmqLg

This is the next best picture I have of the input shaft though

Other pictures and the measurements of the friction disc will need to wait since it's currently at my father's place.

[bornfrustrated]

Measure the clutch plate thickness. I'm not yet convinced the clutch plate has only 14K miles on it. Was the clutch hub extending forward or rearward when it was in place in the clutch pack? Would you post a side profile of the pushrod?

Friction disc thickness is .215"

I have a few pictures of the pressure plate and flywheel. Would it be worth getting a whole clutch kit based on these or just the friction disc?


IMG_20211113_130928.jpg (21.91 kB . 259x576 - viewed 717 times)

[Laitch]

Friction disc thickness is .215"

That's appropriate for 14K miles. If there are no pits or grooves in the pressure plate or clutch cover, what are the conditions of the driveshaft socket splines and the rear drive pinion gear shaft splines that engage with each other? 14K is much too soon for damage to them but take a look.

[bornfrustrated]

If there are no pits or grooves in the pressure plate or clutch cover, what are the conditions of the driveshaft socket splines and the rear drive pinion gear shaft splines that engage with each other?

Driveshaft and rear pinion splines look good.

There doesn't look too be any pitting or grooves. Aside from what looks like where they were machined. What about the spacer ring or clutch nut I see with kits? Should they be replaced while I'm in there?

 And should I pick up a second set of those locating pins for mating the transmission? It has two already but would there be a benefit for adding another set?