Gearbox shaft seal

[(RIP) maverick]

Hello,

Well walked over to my bike last night to find yet another puddle of oil and found that after replacing the bevel drive seals, gear selector seal, fork seals the last month that the freakin gearbox drive seal has started leaking! Arghhhhhhhhhhhhh!!!!

So my question out to you guys is has anyone replaced this seal themselves and is it pretty painless to do? Can it be done without taking the gearbox out? And why if the little black box on a plane is so strong and indestructable could they not build my whole gearbox/engine with it?

Any comments/suggestions kindly appreciated

Cheers

 

[Spout]

Replacing the seal twice on my 100GS failed to cure a leak. I resigned myself to emptying the drive shaft every 500 miles and keeping the gearbox topped up.
Fresh gaitors meant that no oil leaked out of the 'bike'.

Good luck........

 

[(RIP) maverick]

Paul did you do the work yourself or took it to an agent? It did not leak the last 15000 miles that I have had it and like I said this is a recent thing which I take is all due to the 60000 miles the bike has already done. If it is a matter of losening the drive shaft and popping out the old seal from the casing I would love to give it a crack myself. Don't want to re life the bevel drive scenario of stripping off the whole thing realising that I need some special tools to get the oil seal out.

Thanks

Dirk

 

[Spout]

Dirk,
I first discovered the leak a week after buying the bike, so it went back to the dealer I'd bought it off for the fix (or not as it happened).
I was planning on doing it properly myself the second time, but after reading the Haynes manual and needing the bike for work everyday (no alternative transport), I thought it best to let another dealer do it. Had a day off work.
I won't name and shame, but they failed to fix the leak and returned it to me with a loose swing arm.
I'd discovered that the leak was quite small and the weekly routine of emptying the shaft and topping up only took 5 mins (works time) so ran the bike like that for over a year.
I can only assume my output shaft was slightly bent and opened up the new seals after 1000 miles or so.
I did consider getting a reconditioned gearbox but I convinced myself that an oiled paralever shaft was a good thing in light of the reported failures at the time. (I had no leak from the gaitors).


Ride safely...........

Paul W
(Still having to crouch down at the back of my bike every week now I've got chain drive)

 

[Howard Millichap]

I thought about doing this job myself once. Until I read the Haynes manual! It goes on about heating the seal to a certain temperature before pre shaping it over a certain sized arbour and so on. I gave it to a dealer.
They are expected to leak a little because the seal design is out of the ark!!!! It is a spiral laberinth seal rather than a lip seal.
Another reason for it to be leaking though, is that the output bearing is knackered and is stretching the seal, thus letting the oil escape easier.

 

[Mick Fagan]

In the 12 O' Clock position of the hole where the seal sits in, there is an extremely small ventilation hole. This hole is there to allow for the expansion and contraction as the G/box heats up and cools.

If this hole is blocked then the seal mentioned can and more than likely will leak oil.

One needs ones reading glasses on to even see the hole and a magnifying glass to inspect the hole. I have used an old Primus stove prick to clear gunk away from my hole on one service.

Mick.

 

[(RIP) maverick]

Well guys it seems there is various options open for myself and think I will take the whole gearbox out as the thrust bearing is also screaming for attention. So might as well put my foot in it and replace the bearings, seals, clutch plate etc. I was hoping for a quick fix but as with all things you get what you put!
Will however leave this until I return from SA in January hopefully with my R1100GS following closely behind so I am not stuck without wheels. This would allow sufficient time to strip it down and see how far I get before taking all the lose spares to a dealer

Will go with Paul's suggestion although this is going to leave me paranoid of checking the gearbox oil all the time and will need to sort out the gaiter clamp as it is definitely leaking and not so enviro cool!

Thanks for all the suggestions and help.

Cheers

 

[Howard Millichap]

I think Mick Fagan is mistaken. The gear box breather is through the hollow bolt that hold the speedo cable in place.
Also he ought to be very careful when he's pricking gunk away from his hole!!!

 

[Mick Fagan]

Howard, yes the gearbox does vent via the battery earth lead bolt, which also holds the speedo cable on most twins.

The seal between the gearbox and shaft also has a ventilation hole which is the one that I mentioned earlier. It was the cause of some oil shifting between the shaft and gearbox some time ago. After being suitably pricked, no more oil was lost.

Mick.

 

[(RIP) maverick]

speedo cable hole

Ok guys so I have recently sealed the entire section with some silicon etc where the speedo cable enters the gearbox in order to avoid water getting into the gearbox as before. Could this cause the gearbox to build up more pressure and ventilate through the seal?
And to add up to the confusion the stupid thing stopped leaking again since I topped the gearbox oil up the weekend. Did go for a nice long ride and seems to be fine again!?!

I also drained the overfilled bevel drive to a more suitable level of oil as it was pouring through the bevel drive breather onto my tyre. Now this strangely would not happen immediately but only after I have ridden a good 80-90 miles and then stopped for about 5-10 minutes. Only then would the breather start chucking oil at the rubber?? Mick I have seen your solution on the 1100 breather for the vacuum the beveldrive could build up and would think that could be the solution to my problem? Piping it to a small container which it can then suck back at some stage?

Well thinking cap is pretty much been around all positions on me head and will hopefully get to the bottom of this....


Thanks

Dirk

 

[Howard Millichap]

Mick F, I'm pretty sure the seal on the 100GS does not have a vent hole in it. I've had a new seal in my hands and could not see a hole anywhere. However, the 80GS seal could well have a hole as you say. The 80GS has oil in the swingarm so that needs a vent to let out pressure build up. The hole in the seal would let the pressure into the g/box then would vent via the speedo bolt hole.

 

[nobby]

gearbox seal

hi maverick
you need first the thin walled socket to release the swing arm .Then when the gear box is out undo bloody tight nut on out put flange with special tool (made one up) then a puller to take off the output flange can do the seal but need special plate to shim it.if you replace the output bearing when the seal go's the out bearing nnot far behind

cheers nobby( the courier)

 

[(RIP) maverick]

Thin walled socket

Hi Chris,

Uhm any more specifics on the socket as normally go about stripping everthing off then get to the part where I notice a special piece of tool is needed, swear, mutter words in the line of petrol matches set bike alight etc and finally walk or tube to closest place where I can hopefully find said special tool!

Is it a BMW specific tool or do I need to wander through Halfords etc and see if I can find one thin enough to fit?

Oh yes and the silly thing started leaking again just as I started to get happy that it will last that little bit longer.

Thanks

Dirk

 

[Spout]

It's a special BMW tool - a bit like the sort of spanner you'd use on a push bike.
Or you could spend an hour or two grinding the edges of a standard socket.
I've got both. If you want me to post the BMW tool to you e mail me on [email protected] before 3.30pm today.

Paul W

 

[(RIP) maverick]

Socket

Thanks Paul,

Will only be stripping it closer to end October. So if offer still stands will contact you then.

Cheers

Dirk

 

[Paul Young]

Dirk,

I had the same problem on my '91 R80GS in that, I needed it for work everyday so any work had to be started and finished before bedtime.

Rebuilding the gearbox is reasonably easy once you get the output flange off. I live a mile away from Lancs Police HQ and got in touch with their garage. Bingo, one output flange removing tool to borrow whenever needed. The PTFE seals are a bitch to install as they are quite brittle so I used the traditional garter spring type which are also much cheaper and easier to source from any parts factors. I think I bought 5 of them for around £10.

Now, the brilliant idea I got was to find a S/H gearbox which I picked up for £130ish. This way, I could always have one rebuilt and ready to install if the one on the bike had a problem. You can swap a gearbox fairly easily before bedtime and it meant that I could strip/rebuild the broken one at a more convenient time. Find a breaker who doesn't specialise in BMW's but who has an airhead amongst their Jap crap and make an offer. I bought a complete R80 engine from a scrapped Jap bike. Immaculate condition pre-crash and quite low mileage at 21k. The dealer priced fbased on Jap values and I got the entire thing for £300 including all the electrics and carbs. The gearbox was still there when I took the engine so try Fastline M/C in Preston.

I never got a completely dry seal but, as you point out, a little lubrication like this seemed to help as I sold the bike a year ago with 98k miles on it and still running the original shaft with no problems. In fact the bike is now on its way from Istanbul via Sudan to S.Africa and is still on the same shaft today, I believe.

HTH,

 

[Rampant Stallion]

An' don't forget, Paralever seals are fitted with the Garter spring facing in to the g/box, while monolever and just about all other Airheads have their seals fitted with the Garter spring facing out from the gearbox!
Seals can be changed in sittu, depends how tight the o/put flange is... !

 

[(RIP) maverick]

In the 12 O' Clock position of the hole where the seal sits in, there is an extremely small ventilation hole. This hole is there to allow for the expansion and contraction as the G/box heats up and cools.

If this hole is blocked then the seal mentioned can and more than likely will leak oil.

Hi Mick

Yeah mate you were right as mine did have a ventilation hole as you described. Don't think you will notice it if you don't actually look for it. Learned loads after stripping and rebuilding the gearbox and besides struggling without the right tools still loads of fun doing the job. Nearly finished and then I hopefully can make it around the block without gears and bearings flying pass me!

Cheers
Dirk