Tranny issues revisited R80G/S

Discussion in 'Airheads' started by One Less Harley, Mar 23, 2010.

  1. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    As a few might recall my tranny bit the dust coming back from the old school fall rally. Below is a description of what happened.

    I left the motorcycle resort for a much needed off road ride, went up to Star Mountain and did a nice gravel road, I think it was about 40 miles. All was going well, then I got on 68 North and was going to hit some more roads NE of Tellico, but I when shifting into 5th the gear slipped and sounded like the gear was spinning but not engaged???? Very strange. It didn't take long for it to start acting up in 4th (luckily not all the time). Third became noisy sounded like straight cut gears. so no 5th gear and third was sounding bad.

    So I decided to screw the off road stuff and beat a trail back home, 240 miles........ Revs weren't to high in fourth at 55-60, figured if the thing held out...yeah....I should be able to make it home. From a take off I'd start in 1st, hit second ( a little whine from it too) skip third as it was really noisy and go straight to 4th.

    I took the tranny to a reputable guy, very well respected in my neck of the woods, and found out the input bearing was toast..completely trashed, no bearings left.

    I sourced out the parts from MOTO Bins and decided to have it rebuilt as it would be about 600-700 less than a new one from BMW at about $2,600 retail or 20% off from Chicago BMW. If I bought parts from a stateside BMW dealer then the rebuild would have cost more than a new tranny.

    [​IMG]

    Parts replaced were, all the bearings, cluster gear shaft #14, primary gear #4, oil baffle for output shaft, one of the gear selector forks 5th I believe, 3-4th shift cam welded, shift pawl machined, gaskets and seals, taller 5th gear (unknown make, not Kayser).

    So fast forward to the 1st 400 break in miles- I notice a slight whine in all gears, bike shifts well no unusual vibrations. I speak with the re-builder who doesn't seem to worried about it. I don't recall if he said or I just assumed that the new gears might need a little time to mesh w/ the old. So I continue to ride for the 1st 400 miles then do an oil change. Notice a little fuzz on the magnet, but it's not too bad and the oil is a little brassy looking. No big deal I think. So in about 230 more miles my neutral switch starts leaking so I change it out and notice the oil is a little dirty for having only 230 miles on it.
    A quick call to the rebuilder and I describe the oil and whining. He suggest that I bring it to him so he can take a look at it. We both decide that it is best for me to remove it and he'll crack it open and we will see what's going on.
    One thing he noted when the parts were received is the primary gear didn't have the "X" on it, which identifies a 17.5 degree gear, but the part number was correct. He looks at the gear closely and notices that there are wear marks at the top 1/3 of the teeth and not centered as they should, plus the flat side of the gear has some unusual wear marks from where it is thrust against the back of the input shaft (?) when changing gears. (Note the gear's unusual shape, it's designed to absorb the load with the spring).

    This is the only unusual wear noticed, plus since the gear spins at all times in all gears and not just some that would explain the constant noise in all gears. Oh and the ears on #5 have quite a bit of wear on them too. Something is hammering the ears, possibly from the wrong angle of the gears.
    The rebuilder also noted that the input shaft bearing was of an inferior design from the BMW supplied bearing, as the bearing had a plastic cage, plus the inner race was different too.


    The parts we are replacing will be the input shaft bearing with a BMW OEM, and a complete input shaft assembly #2, mathematically it works out being only $65 more for the complete assembly than me purchasing the parts I need individually(#4,5,6,7 and 9). I hope to sell the input shaft to recoup some money. So in hind sight with all the damage and buying the extra parts I should have bought a complete new tranny.

    I'll get pictures of the gear when I pick up the tranny.






    #1
  2. Max Headroom

    Max Headroom lost in the '70s

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    At the risk of contradicting your tame transmission specialist, the plastic cage bearings aren't necessarily inferior to a steel cage bearing at all. In fact, they are often preferable to a steel cage bearing for transmission applications because they are stronger and can cope with the vibration better IMHO. IIRC, most of the airhead OEM gearbox bearings were plastic/phenolic caged anyway. I deliberately chose SKF plastic caged bearings (and a brass-caged 6403) when rebuilding my R90S gearbox, and it's done 12,000mi so far without a hint of a problem.

    I'm suspicious of blame being placed on a bearing supplied by Motobins for a few reasons: for one thing, Motobins are quite sharp suppliers and I doubt they'd supply a substandard product, and secondly it's the responsibility of the assembler to check that stuff before it goes in, not after it's failed.

    I sold bearings for almost 15 years, and quickly made the observation that bearings are a lot like a fuse. If the load specs and service factors are calculated correctly at the design stage, the bearings installed properly with suitable tools/equipment, and the appropriate lubrication is supplied, bearings should last almost indefinitely. If they fail prematurely, then something is wrong! Faulty installation, incorrect preload/clearance, extremes of +/- temperature, contamination, inappropriate or inadequate lubrication, misalignment, or excessive load are just some of the reasons for a premature bearing failure.

    I'd be digging deeper for an explanation from your guy if it were me.

    Just my $0.02c
    #2
  3. Solo Lobo

    Solo Lobo airhead or nothing

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    Did it sound anything like Airhead Wrangler's that got the wrong degree gear? The tech did order the correct one IIRC, but got the wrong one from BMW...

    post number 295 over here...

    Post rebuild mine absolutely whines a bit more than I am comfortable with... and this is three oil changes and perhaps 1,200 miles later.

    Shame on me for sending mine out of state for a rebuild... no way to have it checked by the rebuilder without sending it bacl to CA...
    #3
  4. bgoodsoil

    bgoodsoil Dare to be Stupid

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    I feel for ya man. You know I do.
    #4
  5. Airhead Wrangler

    Airhead Wrangler Long timer

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    Exact same thing happened to me. The guy that rebuilt my box ordered that gear, it came in a bag with the correct part number on it, he put it in and the whining was incredible... like a manual transmission car in reverse. It was bad. I put a total of 1/4 mile on it before I pulled it out of the bike and took it back to the guy that built it. He cracked it open and sure enough there was no 'X' on the gear that he put in, even though it had the right part number on it. He ordered another one from the local dealership. It showed up in a bag with the right part number on it, but again no 'X' on it. We decided to just put the original back in as it only had about 16,000 miles on it. Something's going wrong in Germany. They're supposed to be so meticulous about stuff like that. Hmmm. :huh
    #5
  6. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    MAX- I guess I came across as blaming the bearing for the whining, it was more of an observation that the cage differed from the original. Due to it's location it does get a little side thrust when going into gear or on the throttle. This was pointed out by the re-builder. I chose to be safe rather than sorry on the replacement of the plastic cage bearing.

    The MOST obvious signs of problems was the unusual wear on the primary gear, in such short mileage (about 600). Wear marks already of the top 1/3 or the gear teeth. That concerned me.

    I do trust this man's opinion as he specializes in BMW's and could have asked for money for pulling the tranny apart since I was the one who specified MotoBins for the parts.
    Unfortunately I'm not the only one here that has gotten what appears to be the wrong gear w/o the "x" marks although with the right part #.


    The gear whine wasn't as bad as the Airheadwrangler.
    #6
  7. kixtand

    kixtand Long timer

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    I don't know who your local guy is, but I would be checking w/ Guenther Wuest if'n I were you. Guenther is globally regarded as one of the finest BMW Technicians across the board, and is, in fact, one of the only people I have met that I would allow to work on one of my machines.

    Guenther is located just up the road from you in Fredericksburg, IN.

    kix
    #7
  8. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    Well local in BMW mechanic terms. Yes I know him pretty well, I have confidence in the man. He has given me advice knowing I would probably be doing the work myself. He spent quite a few hours w/ me at no charge on my suspension issues

    If I'm gonna pay someone to work on my airhead it would be him. That says a lot coming from me as I am VERY PICKY on my motorcycles and other vehicles.
    #8
  9. AntonLargiader

    AntonLargiader Long timer

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    BTDT!!

    OK, so I infer the guy who is working on the transmission isn't charging you. That would help.
    #9
  10. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    He charged me for the initial rebuild, but not to pull it apart again and change out the bad parts.
    #10
  11. Rob Farmer

    Rob Farmer Long timer

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    The input shaft bearing was a BMW only special bearing.

    I've seen plenty of 17.5° gears without an X on them and suspect that BMW may have stopped stamping it on the later gears. Just measure the width of the gear at the end of the teeth. 17.5° is approximately 1.35mm while the 15° gears are 2mm - It's very obvious when you have them next to each other.
    #11
  12. mark1305

    mark1305 Old Enough To Know Better

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    Hey OLH, I thought I'd resurrect a couple of relevant posts re the X markings just to refresh everyone following this. I've felt your pain, man.

    Read through the first few posts in the first link regarding the gear angles and X markings.
    http://www.advrider.com/forums/showthread.php?t=430055&highlight=tale+transmissions

    And in the next link, Post #5 shows closeup pics of the primary gears with the hand scribed X and the normal wear pattern on the teeth for that set of gears.
    http://www.advrider.com/forums/showthread.php?t=435511

    Would you buy "good used gears" from this man? :huh :huh :huh

    I apparently didn't take any pics back then of the comparison with the gears in the "newer" transmission that had the X properly stamped into them, but I remember going through both sets and comparing very closely to make sure that both driving cogs and both driven cogs were all the same revised pressure face angle.
    #12
  13. mark1305

    mark1305 Old Enough To Know Better

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    Rob, I can't remember if you've posted that before, but it sounds familiar. In my Tale of Two Transmissions thread linked above, I think I commented that my original gearbox appeared to have been opened/serviced at some point. Your info points to the possibility that some going in there scribed the X on an unmarked gear to clearly identify it for the future.
    #13
  14. Max Headroom

    Max Headroom lost in the '70s

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    Yes it is, but it can be substituted quite successfully for a lot less than the BMW bearing.

    The factory special used a standard NU/NJ204 outer race together with a unique extended inner race. The front oil seal rides on the inner race extension which has an OD of 26.5mm, and this makes substitution problematic. But by obtaining a conventional 20mm x 25mm inner race (intended for needle roller assemblies) and trimming the length to suit, a standard NJ204 bearing can be fitted. The 20mm x 25mm inner race allows the use of a conventional 25mm x 40mm oil seal which is also available in Viton. All of this stuff can be readily sourced from a bearing supplier.

    I have done this conversion on several airhead 'boxes over the last 20 years with great success.

    YMMV etc
    #14
  15. Rob Farmer

    Rob Farmer Long timer

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    By the time you have taken your labour into account wouldn't it have been just as easy to fit a genuine BMW bearing? Only £62.50 for a full set of genuine bearings and a pittance in the grand scheme of things.

    [​IMG]
    #15
  16. Max Headroom

    Max Headroom lost in the '70s

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    Bearing quality is a priority for me. I prefer to use SKF or FAG bearings where possible, and as I mentioned in my first post in this thread I prefer to use plastic/phenolic caged bearings for airhead 'boxes.

    As always, YMMV etc
    #16
  17. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    Hey thanks everyone for the links and info on bearing and gears. Very helpful
    #17
  18. AntonLargiader

    AntonLargiader Long timer

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    Here you go: a 15° gear on the left and an X gear (with broken ears) on the right.

    [​IMG]
    #18
  19. AntonLargiader

    AntonLargiader Long timer

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    Not really. The first X gear had the same square ears as the 15° gear. Later on, they redesigned the whole input shaft and the round and square ears swapped around.

    [​IMG]

    This is a rough approximation of the progression of the input shaft, but the non-X gear is not shown.
    #19
  20. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    thanks for the line up anton!!!! I'm still waiting for the input shaft assembly, none in the states. I hope Germany has some. If not I'll have to get the parts separate.

    I hope to have the tranny in for the old school rally. If not I may have to take another bike.

    [​IMG]

    Damn gonna suck ridding that!!!
    #20