Rear drive worry!

[milleplod]

I thought I'd spend an hour changing the oil in the rear drive today, so set to it with enthusiasm - I've done it every year over the last 6 years, so it holds no fears! My ST has the drain plug in entirely the wrong place, so the unit has to be dropped through 90 deg, which is a bit of a faff really....but hey ho, all relevant bits out of the way, I remove the plug and torque arm bolt and drop the unit for it to drain. As I watch the old stuff come out, it occurs to me that there doesn't seem to be as much as the 180ml I'm about to put back in! I leave it for a good 30 mins to drain....and there's only around 100ml come out! I optimistically wiggle the drive about a bit to see if any more's hiding in there....but there isn't.

So....where's it gone?? There's no leak anywhere that I can see - I removed the rubber boot completely, it was mucky in there, but nothing like oily, not what I'd expect to see if there'd been a leak. Did I underfill it last year? I'm a bit paranoid about oil levels and stuff tbh, I use a syringe to measure what's going in, and even lock myself in the garage so I don't get distracted during the filling!

Also, the oil looked a bit darker than I remembered last year's old stuff looking - that could be my memory failing though! I've just looked at JVB's guide to doing the oil change, and tbh mine was no darker than the stuff coming out of his bike in the pics.

I'm now going to have sleepless nights worrying that the rear drive unit's buggered!

Pete

[Herb]

I wouldn't lose too much sleep. If its not leaking, no bits in the oil and no play, feels smooth etc then I am sure all is OK.

Maybe you did underfill it? I use a syringe from the vet, but it only takes 60ml, so I have to give it 3 shots, in the past I have lost count (getting so old I cant count to 3).

I would refill with the correct amount of fluid. Ride it for a 1000 miles or so, then drain and fill again so you can check the oil condition.

FYI, my oil is always black, but its a bit weird, like the oil has separated, so it looks like black ribbons running through clean oil.

[milleplod]

Thanks for the quick reply, appreciated.

Definitely no bits in the old old oil, and yes, that's just how I'd describe what came out of mine - some good-as-new looking stuff, some a murky mess! My syringe only does 20ml at a time....I have to count all the way up to 9! I'll do what you suggested - off to Spain in May, so could do with that 'peace of mind' feeling before then!

Pete

[Herb]

Go to your nearest vet and ask for their largest syringe. 20ml, be there all day.

[milleplod]

I was. almost....my back's killing me! I trod on my large syringe and never got round to replacing it.....there's a vet supply place opposite my Mrs's shop, I'll be calling in tomorrow!

[fontana]

If there was a bevel box oil leak, I would have thought it would be obvious.
It's only got two ways out.
Through the rubber boot via the pinion seal, or out the inner radial seal onto the wheel and tyre.
That happened to an R1200C I once owned and it's pretty scary if you don't spot it in time.

[Humbug]

Not sure why but Mike from Overland told me to ignore the 180ml specification and put 200ml in when he rebuilt the final drive on my 12S. Maybe he knows something we don't.

[milleplod]

Not sure why but Mike from Overland told me to ignore the 180ml specification and put 200ml in when he rebuilt the final drive on my 12S. Maybe he knows something we don't.

I have read that elsewhere. I'm going to try to put a few miles in over the next week or so, then drain the unit and refill it, and I'll go with the 200ml this time. I'm 100% certain there's no leak, so perhaps I managed to underfill it last time - hopefully I've not damaged anything!

Pete

[Herb]

Not sure why but Mike from Overland told me to ignore the 180ml specification and put 200ml in when he rebuilt the final drive on my 12S. Maybe he knows something we don't.

I have read that elsewhere. I'm going to try to put a few miles in over the next week or so, then drain the unit and refill it, and I'll go with the 200ml this time. I'm 100% certain there's no leak, so perhaps I managed to underfill it last time - hopefully I've not damaged anything!

Pete

Without criticizing Mike, I am sure he has forgotten more about these final drives than I will ever know, but why would you ignore the recommendation of BMW? Despite getting it wrong the first time, they still have thousands of hours of test data on these drives, plus the feedback from all of the field failures and warranty returns on the failed bikes.

I will stick with 180ml or whatever BMW currently recommend.

The original fill was 220ml. The current recommendation is 180ml, maybe people think 200ml is some kind of perfect compromise?

[milleplod]

Without criticizing Mike, I am sure he has forgotten more about these final drives than I will ever know, but why would you ignore the recommendation of BMW? Despite getting it wrong the first time, they still have thousands of hours of test data on these drives, plus the feedback from all of the field failures and warranty returns on the failed bikes.

I will stick with 180ml or whatever BMW currently recommend.

The original fill was 220ml. The current recommendation is 180ml, maybe people think 200ml is some kind of perfect compromise?

Fair point, but perhaps he just gets to repair units that BMW have no knowledge of and bases his recommendation on what he sees? There are a hell of a lot of bikes out there that won't be 'contributing' to BMW's database, mine included - if it fails, BMW won't ever know, but someone like Mike will....and he'll have an explanation for it and a recommendation as to how to help prevent it failing again.

Pete

[Herb]

I'm not convinced. Any individual will see a handful of these for re-work, he might even see 1 or 2 a week from all the models of R1200 and K that share the same, or similar (in the case of the K) designs.

BMW will have warranty data on thousands of bikes from all over the world. Despite the initial problems, I would put my faith in the manufacturers recommendation on this issue, rather than because some bloke said.

When this failure happened, BMW will have followed a systematic approach to identify the route cause of failure, and they will back this up with testing, including accelerated life testing at different oil fills prior to making a recommendation.

[Humbug]

I agree Pete, Mike showed me some drives he had around that were sent to him with various levels of oil in them including one with none at all! It was one that he had rebuilt and sent back to the customer by post with instructions on filling. The chap had assumed it was already full despite the hole in it for the sensor and the instructions and fitted it to the bike. He wondered what the noise was after about 30 miles . Mike gets to see a lot that BMW may not, I would certainly not be looking to highlight my idiocy by putting my bike into a main dealer.

[dave the german]

Maybe 200ml after a strip down? that makes a bit more sense?

[milleplod]

Maybe 200ml after a strip down? that makes a bit more sense?

A good point indeed!

Pete

[Britisherspy]

Shit I've filled mine up to the filler hole, same as the gearbox. Shall I drop it and start again?