Airhead Gearbox Woes

Discussion in 'Airheads' started by kougan, Feb 18, 2013.

  1. kougan

    kougan Been here awhile

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    I had written a very long-winded story of what happened with my /5 and my process of diagnosing it, but unfortunately this site logged me out as I submitted. So I'll save you time and give you the short version:

    Riding at highway speeds for an hour and a half. Stopped for a pitstop, started the bike up again and heard a very loud, disheartening grinding sound. It stopped when I pulled the clutch in, then resumed as I let it out. Towed it back home and thought it was either the clutch or gearbox. Took the gearbox out (a 5-speed installed by the P.O., not 4-speed) and found:

    1. Water mixed with the gear oil
    2. No felt on the pushrod, pushrod a bit rusty. Perhaps water and oil leaked into the clutch, causing a mess?

    Bearings look a bit "burnt" on the sides, as do their insets in the casing cover. They roll fine though. Got the input shaft out fine, but cannot, for the life of me, get the other two out. Any suggestions on getting these out? Don't know if there is a circlip involved or not. The input shaft has an "X" scratched into it. Should the other two shafts have Xs also?

    Does this grinding situation sound familiar to anyone?
    Next will be checking the clutch out.


    <a href="http://www.flickr.com/photos/ecumalander/8486927191/" title="BlackenedBearings by ecumalander, on Flickr"><img src="http://farm9.staticflickr.com/8093/8486927191_c333ecb207.jpg" width="375" height="500" alt="BlackenedBearings"></a>
    <a href="http://www.flickr.com/photos/ecumalander/8488018540/" title="Insets by ecumalander, on Flickr"><img src="http://farm9.staticflickr.com/8250/8488018540_999a85b046.jpg" width="375" height="500" alt="Insets"></a><a href="http://www.flickr.com/photos/ecumalander/8488019048/" title="Clean by ecumalander, on Flickr"><img src="http://farm9.staticflickr.com/8523/8488019048_5d5bf50ab9.jpg" width="375" height="500" alt="Clean"></a>
    #1
  2. disston

    disston ShadeTreeExpert

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    It appears you have a kick start 5 speed. So this would be a 1974 5 speed maybe? Do you know?

    You say there is an X on the input shaft? Where? I mean where is this X. If you are thinking these might be X gears, they might but the X is on the angle cut gear only, not on the shaft.

    To get the other shafts out heat the case with propane torches. Usually use two torches because it takes a lot of heat. I use Mapp gas in my propane torch it burns hotter. If you have Acetylene you have to be careful to not get the flame too hot and melt a hole in the case. Heat the case with the opening down and the shafts will fall out.

    The blackening on the bearings is not a problem. Check bearings for lateral movement, looseness. And roughness.

    You should be prepared to reshim this box but did you catch the shims that were in it so you know where they were?

    The noise you describe sounds like it's from the clutch. Was it louder when driving or just at idle?
    #2
  3. kougan

    kougan Been here awhile

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    Thanks, Disston. It is a kickstart, though I'm not sure on the year. I'll have to check for a serial number.
    And yes, the X is on the shaft. I haven't spotted any on the gears. So if it's on the shaft, then its not the revised gear angle? Wow, confusing.

    I tried heating with a torch, although with a page full of warnings against it in Clymer's I just went for *light* heat. I'll give it a little more and see if that does the trick.

    The bearings aren't really loose at all, and I did mark all the shims, so all in all, the gearbox might be fine. There was a little oil seal piece sitting on one of the bearings that I misplaced thought, so hopefully that's not an issue.

    The grinding was louder when driving than at idle, though i only took it a few feet for fear of decimating some internals.

    Thanks for your help, I'll have to get into the clutch.
    #3
  4. disston

    disston ShadeTreeExpert

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    I don't know what to tell you about the box. The front bearing on the out put shaft is usually the first to go so you want to check that one and it's still in the case. Don't know about Clymer's warning about heating the case. I wonder how they think you are going to get the bearings out? It's not just Clymer's manuals that have weirdness tho, it's all manuals. I've found weird stuff in Ford Shop manuals.

    Yep sounds like oil or grease on the clutch? Rear engine seal been leaking? Have you recently lubed the splines just before this happened? Take the clutch out. You can clean them and they usually work pretty good but the last time I over greased my trans splines and did this it was a ten year old clutch so I replaced it.

    Oil seal? You found part of an oil seal? Would this be the trans front oil seal? A source of oil on the clutch if it is.
    #4
  5. bikerfish

    bikerfish flyfishandride

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    if it were mine, I'd replace the bearings, you already did most of the work! new bearings , reshim, new seals, and you'll have a box that you KNOW is good to go for a long time.
    the problem may be in the clutch, worth checking out since the tranny is out of the way, might as well check the main seal and oil pump o-ring as well since your there, replace if needed.
    from the symptons you describe, it sounds like a bad input shaft bearing. I don't trust the old "hand" check method, you just cant duplicate the forces on a bearing by spinning it in your hand. I've had noisy ones that felt fine when I took them out, but after replacing them, the noise was gone.
    oil on the clutch is gonna make the clutch slip, but I've never heard any grinding noises from that. worn rivets will make some noise though, but from the ones I've heard, it's more of a rattle, not grinding.
    #5
  6. Fast Idle

    Fast Idle Since the Sixties

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    The warnings on heating the case and cover are about NOT using a torch as it can warp or otherwise cause damage. Do yourself a favor and buy a heat gun and a laser point thermometer. Both are relatively cheap these days. These are a mechanics best friend, well besides the BFH. Anyway you can easily and evenly heat the case with the heat gun and check the temps with the the thermometer. I find everything comes apart fairly easy around 180 degrees but I believe BMW calls for 212. It works great for changing the bearings too. Heat them and they come off easy. Heat the new ones and they go on easy. You'll also need to heat the cover for reassembly and the end play measurement game as well. Seriously buy a heat gun and you won't believe how you ever got by without one, a must have tool for this kind of work! :1drink
    #6
  7. Airhead Wrangler

    Airhead Wrangler Long timer

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    Make sure you get one with the little stand that allows you to set it up to heat something without you having to hold it. That way you can let something heat for a few minutes while you're doing something else.
    #7
  8. Rob Farmer

    Rob Farmer Long timer

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    Did the clutch work ok or did it grab a little?

    I had the spot welds on my clutch come adrift a few years ago made the clutch grabby and also made some very strange noises but appeared to work fine apart from those issues. When It finally got to the point that it wasn't adjusting properly I pulled the gearbox and found the pushrod snapped and the pop rivets all adrift. I'd check the clutch while your in there. You can see the chatter marks on the clutch plate.

    [​IMG]
    #8
  9. Padmei

    Padmei enamoured

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    It took a LOT of heat to get my bearings out - much more than my mechanic friends were happy with. My gas torch wasn't grunty enough. I ended up having to use a slide hammer around the bearing to get one off & the other fell out at the same time. I'm not advising you to do this but pointing out they can be buggers to get out.
    #9
  10. ME 109

    ME 109 Long timer

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    I'm a heat gun supporter as well.

    Not so sure I like the blackened bearings. Would it not show that the bearings have been spinning in the cover?

    I wouldn't put it back together without changing the bearings. They are reasonably cheap.

    A thorough rinse of all shafts and selector mechanism in a tub of petrol (or proper safe fluid :deal ) to remove any crud.........there will be crud.
    #10
  11. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    #11
  12. kougan

    kougan Been here awhile

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    I agree with you on the bearings possibly spinning in the cover. May as well replace them while I've got the box open, along with the springs, which I've heard tend to fail in time. Everything else looks to be fine though. I'll take the advice and try a heat gun on the other two shafts. The torch isn't cutting it.

    The clutch did seem a bit grabby, but again, I really didn't test it's rideability, for fear of making symptoms worse.

    Looking at your pic of the chatter marks on the clutch plate, I'm thinking something similar happened in my case. Hopefully I can find the time to get to that clutch this week.
    #12
  13. ME 109

    ME 109 Long timer

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    It will take a few minutes to heat up enough with the heat gun.
    Once in the vicinity of the necessary temp, use one hand to pull/rattle the two shafts while continuing to heat the front of the tranny.

    Don't use loctite or similar to retain the bearings in the cover!
    If the bearings are spinning in the cover (and it looks to be the case) they will be grinding away at the shims as well.

    The cover may be toast??
    #13
  14. kougan

    kougan Been here awhile

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    I'm wondering where any of you have found cheap bearings...or bearings at all for that matter. There's no shop locally in my area that carries what I need and I haven't found any online besides ebay, and those don't seem exactly cheap to me.

    I tried a heat gun, then back to the torch again, then heat gun again, and still no luck getting the remaining two shafts out. So I think it's safe to say the bearings on that end aren't going to be spinning around in there, unlike the other ones. I'll just leave them alone and replace the three. Those, along with the springs on the selector mechanism.

    Got the engine out of the frame and will be examining the clutch this week.
    #14
  15. Solo Lobo

    Solo Lobo airhead or nothing

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    Call any BMW dealer, or commerical bearing supplier.

    Anton lists the bearing specs here: link
    #15
  16. disston

    disston ShadeTreeExpert

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    Those shafts should by all means come out. Use a large rubber mallet to beat on the case and use more heat. I know that you are all afraid of causing damage, I don't want to cause any damage either, but they will come out. You can also be too timid with these things.

    Order all the trans parts you need from Ted Porter's Beemer Shop. You will have to call them on the phone. They don't have everything listed on their web site but they will have the parts and they will be cheaper than the dealer. This is the good deal on the correct parts. You may save more at other places but you need the correct parts. Do this. For transmission bearings and parts use The Beemer Shop.

    http://www.beemershop.com/

    Sometimes Ted answers the phone himself. Ask him about what I said about beating the shiete out of this case and getting those shafts out.

    I would try to make the order very soon. Everybody is going to be getting very busy in only a few weeks. Right now is the time to do this.
    #16
  17. kougan

    kougan Been here awhile

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    Solo Lobo - SUPER helpful link from Anton, thanks.
    Disston, that's the confidence booster I needed to keep pounding on that case! I kept imagining cracking a blackened, warped case before I got the things out.
    #17
  18. disston

    disston ShadeTreeExpert

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    BTW, I don't know why but in the beginning of your thread I was under the impression that you were trying to do this with out spending any money, i.e. saving all the bearings and fixing the problem and so on and so forth. It is never advisaeable to try and repair things especially Getrag transmissions this way. Get all the bearings except the front bearing on the input shaft, if it looks serviceable now (you have the input shaft out, you should be able to tell if it is OK, this bearing does not always get replaced).

    Get all the seals and the rear cover gasket at The Beemer Shop. Get anything else they say you need. That's their job.
    #18
  19. kougan

    kougan Been here awhile

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    While I'd love to keep this at an economical level, I don't really think it's an option ha. I'll take any advice they can give me and replace what they say, as I don't want to have to crack this box open again any time soon.

    "I'm going to need new gold-plated casing? Okay whatever you say."
    #19
  20. Solo Lobo

    Solo Lobo airhead or nothing

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    If this is the case you may want to do the front bearing on the input shaft
    #20