Gearbox input splines & crankshaft seal?

[MikeB]

I took the gearbox off my R1100S today in order to check the clutch and noticed some uneven wear on the gearbox input splines - see picture below. I would estimate that the splines have worn up to a third of the width of each tooth but only corresponding to the outer edge of the clutch plate splines.
When I put the clutch plate onto the gearbox input splines I can see and feel some slight radial movement that results in no more than +/- 1mm (total 2mm) at the circumference of the plate
When restored, the bike won’t be doing massive mileages so can I get away with replacing the clutch plate with one with an extended spline or am I looking at a gearbox rebuild?

Also, there is no evidence of any leakage around the crankshaft oil seal so is this best left alone or is it one of those, ‘while I am in here’ jobs. The bike has done 35000 miles.

As usual, I would be grateful for any opinions or advice.

Many thanks

Mike

[andys]

I used to spend endless hours researching and worrying about input splines, not helped by BMW guru Chris Harris videos on YouTube.
In the end I just put the whole thing to bed and decided if it goes it goes.
Shortly after that I got to see an 1100RS like mine having its clutch done at the dealers.
It had 80,000 miles and the splines looked fine.
The mechanic said there was no significant wear.
I'm no expert but those teeth don't look too bad but if it were me I'd definitely replace the rear main seal.
It seems daft not too while its accessible.

[MikeB]

Thanks Andy,

You are absolutely correct, watching too many videos on the subject or reading too many horror stories on various forum is not healthy. I have measured the radial movement of the clutch plate using a pointer and it is a millimetre in total rather than the 2mm reported yesterday so I am going to save the cost of an input shaft replacement and concentrate on replacing the entire clutch as the pressure and cover plates are significantly dished.

Thanks for your advice regarding the crankshaft seal. Again, you are correct, there is a slight weep at the bottom of the seal - see below - so I will replace it. The question is, should I replace both the inner and outer or am I safe replacing just the outer? I understand that the outer often leaks due to crankcase pressure, whereas the inner is not affected due to being on the engine side of the breather passage.

As usual, any advice will be gratefully received.

Take care
Mike

[Mjolinor]

I hope you have the front of your crank chocked on that picture.

[MikeB]

No I haven’t.
I thought that was only the airheads that need securing and there is no mention of it in my Haynes manual.
Have I broken it?

[Mjolinor]

Yup, sorry. My bad. That's what reading "new posts" does for you.

[MikeB]

Phew!

[King Herald]

I used to spend endless hours researching and worrying about input splines, not helped by BMW guru Chris Harris videos on YouTube.
In the end I just put the whole thing to bed and decided if it goes it goes.
Shortly after that I got to see an 1100RS like mine having its clutch done at the dealers.
It had 80,000 miles and the splines looked fine.
The mechanic said there was no significant wear.
I'm no expert but those teeth don't look too bad but if it were me I'd definitely replace the rear main seal.
It seems daft not too while its accessible.

From what I’ve seen the BMW splined output shaft is not a lot smaller than the shaft on many V8 cars, yet none of them seem to suffer the dreaded worn spline issue. Is there a particular reason for the wear, poor/no heat treatment etc?

[Mike D]

There was some debate years ago about the input spline problem.

One reason given (but not admitted to by BMW) was that one of the Getrag fatories (who made all of the BMW gearboxes) had a misaligned jig. This meant that the locating dowel holes were fractionally off. This put pressure on the shaft leading to premature wear. This could be remedied by the manufacture of an offset dowel. However to do that required some accurate measurement of the centreline and dowel position to establish the amount of miss-alignment.

The depth of spline engagement of the clutch centre was also questioned. The input shaft does not full protrude through clutch spline. It was considered that this allowed a slight rocking movement of the clutch, not helped on the R1150 by owners running in top (6th) gear at lowish rpm.

The problem usually occurs at low mileage (mine went at 16,700 miles), if a gearbox has covered 25-30k miles and not had a problem, then it should last for many more miles.

The following photos are from my gearbox.

Mike

[MikeB]

Thank you Mike,

That is very interesting. Have you any ideas why the wear on the input shaft only occurs closer to the gearbox when the outer end of the shaft is perfect? (on mine it is anyway).
The clutch centre on mine doesn’t show any signs of wear so do you think that it is possible that the wear to the input shaft won’t get any worse now?

Mike

[Mike D]

If you look at your I/P shaft the wear is from the end of the shaft, the portion nearest the gearbox not damaged because it does not come in contact with the splines of the OEM clutch plate. You can fit a different clutch plate from Motorworks which has a longer boss that does engage with more spline length. It is supposed to help prevent the problem. It wasn't available when I did mine. I had to replace the I/P shaft (and bearing) but used a OEM plate, in fact looking at my notes and invoices I replaced the whole clutch assembly.

Do you know if your plate been changed before?

When you measured the radial play, was the clutch plate pushed on to the I/P shaft so that it was either flush or protruding from the plate. If so you need to recheck with the shaft only into the pate for about 3/4 of the spline depth (as it would be when in use).

If it's still minimal I would would be tempted to replace just the plate with the modified version. Bear in mind that it's a fair bit of work to get to where you are now, and you don't want to do the job again!

Mike

[MikeB]

Again thank you Mike,

I don’t think that the clutch has been replaced on this bike because everything looks untouched and the bike has only done 35000 miles. The friction plate also doesn’t look too badly worn but there is dishing on the fixed plates so unless you or any of our friends have any advice I will replace the whole lot, using one of the friction plates from Motorworks with the extended splines. The full length spline seems such an obvious thing to do, it is surprising that BMW didn’t fit them, but hey-ho, it keeps an old man in his garage on cold Winter nights I guess.

When I checked the radial movement of the friction plate I measured it with the plate at either end of the input shaft and in the middle. The results are surprisingly consistent at 1mm. I guess the the splines must be bridging the gap in the wear?

I will also replace both rear crankshaft seals because I can see some slight seepage and it would be silly not to. Did you do the same on your bike and if you did do you have any advice?

Stay safe
Mike

[bazzzer]

Mine went at 55k.
Doing 77mph on local bypass, all fine. 2 miles of town work and suddenly the dreaded durrrrrrrrr and no drive. When stripped the input shaft didn't look too bad, but spun freely inside clutch (clutch plate itself had plenty of meat left). For the hassle and inconvenience of a breakdown (the week before i was in the south of France) i would change the shaft and do the extended spline clutch plate

[MikeB]

Hi Bazzer,
Sorry to hear about the issues that you experienced. It must be really shocking to find that the clutch splines are gone. In comparison, mine are very good but the plate itself is worn so I will definitely replace it with one with extended splines.
How difficult is it to change the input shaft and it’s bearings?

Stay safe
Mike

[Mike D]

I Didn't replace my rear main seals as there was no sign of any leakage. I did however need to replace the clutch master cylinder.

To replace the input shaft and bearing is a complete gearbox spit and rebuild. I had it done by a guy who was well known for his work on gearboxes and rear bevel drives. I spent a day with him while the job was done. This included checking the endfloat for the correct clearance. The physiocal strip and build is easy enough (if you are mechanically minded), but measuring the stack heights takes some decent measurement kit. It's not as easy as an airhead boxer, that's for sure! One of the first things he checked was the make of the rest of the gearbox bearings to make sure they were a reputable make.

When I bought my input shaft (2011) it was £190 inc. VAT.

As I run the BMW Club's Tool Hire facility I had the rear seal tools available should I have wanted to replace them.

Mike

[MikeB]

Hi Mike,
Thanks for this interesting information. I think that I am going to pass on replacing the gearbox input shaft after reading your note. I don’t have a press or suitable measuring equipment so the shaft will stay as-is and I will replace the entire clutch, using a friction plate with extended splines.
My outer seal is leaking so will need to be replaced and so it is very useful to know that the BMW Club have a tool hire service, thank you.

Stay safe
Mike

[andys]

Thanks Andy,

You are absolutely correct

Mike

OK to be absolutely clear, I am not an expert and was not trying to give out advice.
I apologise to all here with real knowledge, if I inadvertently gave that impression.
Matters such as these go way beyond my remit as someone who's spannering skills don't extend beyond changing the oil and adjusting tappets.
Everything else has to go to a mechanic.

[MikeB]

Hi Andy,
There’s no need to apologise because in a lot of cases even the smallest piece of advice sparks another train of thought that can be extremely useful. I also think that it’s worth pointing out that I was agreeing with you in that watching certain YouTube videos can, in some cases be unhelpful and cause unnecessary worry.
I don’t plan on using this bike to circumnavigate the World and so simply replacing the clutch at this stage should be fine and then if at some point in the future I have to strip it all apart again for whatever reason, then that is entirely down to me.

Stay safe
Mike

[Mike D]

If you ever need to outsource gearbox or rear bevel drive repairs then Mike Overy at Overland & Classics is very highly recommended. he is based in the Vale of Belvoir, so postage could be an issue.

Mike

[MikeB]

Thanks Mike,
That’s really good to know. The splines on my RS bevel drive will need to be done in the next year or two.

Take care
Mike