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Thread: Clutch and input shaft spline - need advice please

  1. #151
    Curmudgeon nrpetersen's Avatar
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    Tight spline and more engagement should make for lower contact stress and less relative sliding motion/wear between male/female splines?

    What happens to the rear main bearing radial load if you move the hub closer to the trans?

    The relative ID to OD sliding motion of the spline teeth is determined by the radial misalignment minus the tiny bit of shaft and housing deformation, minus the radial clutch disk slippage on the flywheel face. The number of teeth doesn't make any significant difference. Few big teeth vs many small teeth - all the same unit loading. After a while the main bearings wear until the crank can establish a new operating centerline.

    The rear main bearing loading will be limited by the clutch disk-to-flywheel friction. I don't think moving the spline hub will affect it much.

    I suspect the reason BMW has not done anything callback-wise is that there is no way they can easily check alignment without a horrendously costly disassembly. And even if 10 percent of the bikes eventually will fail (my WAG), most will be out of warranty such that they can just tough it out.

    Just how bad is your old input shaft spline? It does not have to be perfect to get a lot of miles out of it - especially if there is no relative motion/radial misalignment. Have you got a clear photo of it?
    Retired w 2005 K1200LT, 2000 R1100RT, & 1975 R90/6

  2. #152
    Registered User roger 04 rt's Avatar
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    Quote Originally Posted by 2dflier View Post
    Tight spline and more engagement should make for lower contact stress and less relative sliding motion/wear between male/female splines? My head is starting to hurt. Too many moving parts.

    ...
    Couple that with the angular geometry introduced by the hypothesized straight radial offset. In other words if you hypothesize the the transmission is shifted down, the the clutch disk has to either: slide around during rotation; or the clutch web has to flex at an angle. The later seems more likely and more consistent with the wear pattern on the input shaft--more wear on the inboard portion. In that model a greater insertion and tighter connection matter, meaning that more insertion helps.

    Your point about a tighter connection meaning less sliding and wear is a key idea. After all it takes "work" to wear the surfaces, and "work" is "force" times "distance". So less sliding "distance" has to mean less wear.

  3. #153
    Registered User 2dflier's Avatar
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    Quote Originally Posted by nrpetersen View Post
    Tight spline and more engagement should make for lower contact stress and less relative sliding motion/wear between male/female splines?

    What happens to the rear main bearing radial load if you move the hub closer to the trans?

    The relative ID to OD sliding motion of the spline teeth is determined by the radial misalignment minus the tiny bit of shaft and housing deformation, minus the radial clutch disk slippage on the flywheel face. The number of teeth doesn't make any significant difference. Few big teeth vs many small teeth - all the same unit loading. After a while the main bearings wear until the crank can establish a new operating centerline.

    The rear main bearing loading will be limited by the clutch disk-to-flywheel friction. I don't think moving the spline hub will affect it much.

    I suspect the reason BMW has not done anything callback-wise is that there is no way they can easily check alignment without a horrendously costly disassembly. And even if 10 percent of the bikes eventually will fail (my WAG), most will be out of warranty such that they can just tough it out.

    Just how bad is your old input shaft spline? It does not have to be perfect to get a lot of miles out of it - especially if there is no relative motion/radial misalignment. Have you got a clear photo of it?
    I didn't take any pictures of the input shaft splines. There was definitely wear - maybe more towards the middle - but there looked to be plenty of meat left. The trans had been rattling in neutral for 20K miles and started making something of a grinding noise going down the road the last couple of hundred miles, which is why I pulled the trans. It's currently at the local shop waiting to be looked at - for over a week. So I didn't really bother too much with the spline thinking that the case would have to opened up and bearings replaced. The shaft I figured would just get replaced. The clutch splines were much more concerning. I figured it was just a matter of time before I was sitting on the side of the road wondering why I didn't pop for towing...

    Spline Wear.JPG
    May the road rise to meet you...

  4. #154
    Curmudgeon nrpetersen's Avatar
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    I think you take the record for getting home while being closest to a total spline strip out. Your luck has been pushed. Don't expect any more!

    Try to recover the shaft. If nothing else, I'd like to check its hardness profile. (I have local friends that can get us Rc measurements)

    This is a pretty clear case of the wear profile including the effects of the disk spider being flexed. A greater engagement would have postponed failure some, but the real problem remains the radial alignment error. The new pin offsets (if you want to go that route) should take the rear main bearing wear into account because the clearance makes the crank run on an average new centerline.

    You have a choice - find another transmission on ebay, or fix this one and I'll make up offset pins. Do you want the alignment check fixture (the blue thing with a dial indicator on it per SpaffyPD's postings)? I'll need a shipping address.
    Retired w 2005 K1200LT, 2000 R1100RT, & 1975 R90/6

  5. #155
    Registered User 2dflier's Avatar
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    Quote Originally Posted by nrpetersen View Post
    I think you take the record for getting home while being closest to a total spline strip out. Your luck has been pushed. Don't expect any more!

    Try to recover the shaft. If nothing else, I'd like to check its hardness profile. (I have local friends that can get us Rc measurements)

    This is a pretty clear case of the wear profile including the effects of the disk spider being flexed. A greater engagement would have postponed failure some, but the real problem remains the radial alignment error. The new pin offsets (if you want to go that route) should take the rear main bearing wear into account because the clearance makes the crank run on an average new centerline.

    You have a choice - find another transmission on ebay, or fix this one and I'll make up offset pins. Do you want the alignment check fixture (the blue thing with a dial indicator on it per SpaffyPD's postings)? I'll need a shipping address.
    My luck usually doesn't run that way so maybe I should start playing the lottery again.

    Many thanks for the offer to make a set of offset pins. Given more time to play around, less need to get the bike back on the road, and a desire to extend the service life, I'd investigate this much deeper. It's interesting. But 90K+ miles without intermediate spline maintenance has to be good enough for now. I really have no expectation of keeping the bike for that long. The trans is out for repair but I will be sure to retrieve all replaced parts and would be happy to ship you whatever you'd like to see - including clutch parts. Speaking of time... Late for work.
    May the road rise to meet you...

  6. #156
    Registered User froggy's Avatar
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    This past fall my splines shredded at 32000. Pulled trans and had my mech. install new shaft and seals (did not replace bearings due to mileage), the friction plate was like New except the hub. Bought the hub extender, bought oil soaked friction plate off of inmate on this site and switched out his good hub with my threaded hub. So I was able to 're-use my friction plate with adapter installed and it only cost me shipping of the oil soaked plate and cost of adapter. Told mechanic to give me old shaft and I used that as my alignment tool. Have ridden it hard for the last 1500 miles and only problem is a whining in trans in all gears and idle. Is it the front bearing on trans- I don't know... asked my mech and he said that "gear teeth are not in same spot and will need to brake in". True, not true, not sure but fact is I'm NOT pulling that trans back out. What a pain in the $&#@&$ that is.
    We drove all this way for a DEAD END ! My son!!!
    02 Silver RT1150 My 1st BMW Bike ...Totaled 2/23/16
    13 Black R1200RT 90th Annv
    Craig

  7. #157
    Registered User 2dflier's Avatar
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    Quote Originally Posted by froggy View Post
    This past fall my splines shredded at 32000. Pulled trans and had my mech. install new shaft and seals (did not replace bearings due to mileage), the friction plate was like New except the hub. Bought the hub extender, bought oil soaked friction plate off of inmate on this site and switched out his good hub with my threaded hub. So I was able to 're-use my friction plate with adapter installed and it only cost me shipping of the oil soaked plate and cost of adapter. Told mechanic to give me old shaft and I used that as my alignment tool. Have ridden it hard for the last 1500 miles and only problem is a whining in trans in all gears and idle. Is it the front bearing on trans- I don't know... asked my mech and he said that "gear teeth are not in same spot and will need to brake in". True, not true, not sure but fact is I'm NOT pulling that trans back out. What a pain in the $&#@&$ that is.
    I guess gear whine makes sense. The front input bearing finally going out save me from totally stripped splines. They were close but after 95K miles the friction disk was hardly worn. But the clutch housing and pressure plate were worn so the whole thing had to be replaced. I'm just waiting on the new clutch servo to finish up the install but when it comes time for a spline lube I'm thinking a day trip to a professional. It's more than a day job for me and removing the trans is not something I want to get good at.
    May the road rise to meet you...

  8. #158
    Curmudgeon nrpetersen's Avatar
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    Quote Originally Posted by froggy View Post
    Have ridden it hard for the last 1500 miles and only problem is a whining in trans in all gears and idle. Is it the front bearing on trans- I don't know... asked my mech and he said that "gear teeth are not in same spot and will need to brake in". True, not true, not sure but fact is I'm NOT pulling that trans back out. What a pain in the $&#@&$ that is.
    Gear teeth only wear to a more noisy condition. You must have a worn/loose input bearing.

    And gear teeth should not have to "break in". I once had a 1:1 set of noisy high speed gears on an industrial application that I tried to wear in with lapping compound. That didn't work at all & a gear guru explained why.
    Retired w 2005 K1200LT, 2000 R1100RT, & 1975 R90/6

  9. #159
    Registered User froggy's Avatar
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    Did check for looseness in front end of trans before handing it to my mech. DoddDmmDoddD not check too closely due to mileage and trans was quiet prior to input shread, only told him to replace all seals.
    We drove all this way for a DEAD END ! My son!!!
    02 Silver RT1150 My 1st BMW Bike ...Totaled 2/23/16
    13 Black R1200RT 90th Annv
    Craig

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