Final Drive and driveshaft splines - your esteemed opinion

[Motorhobo]

Hi everyone -- with the weather now above 50 deg (temporarily --ugh) I got  a chance to pull the final drive and driveshaft off the 94 K75 I bought in August to ride while restoring my 95 K75 main squeeze. What I found in there was like looking down the hole in a porta-john.




First question -- why anyone would let this happen -- is moot. Second question -- what is all that rusty crap and how did it get there -- well, I'd kind of like to know if that's normal if you never open it up and clean it out. Is it indicative of a bad seal somewhere? There was no liquid gear oil in there, just crud. It looks like any moly paste had been flung off the shaft ages ago and was just coagulating and collecting crap on the interior of the case.

But to the condition of the splines -- here they are after a bit of cleaning.





And the driveshaft, input and output sides.




So now the $40K question -- how bad do they look? Percentage-wise, how worn are they? And if I lube them up with Guard Dog every 6K miles, how long can I expect to ride before hearing that horrible gnashing time-to-get-a-trailer sound?

BTW, this final drive has a bit of radial play, maybe a mm, when you hold the disk steady and turn the shaft you can turn it a wee bit but not when you try to wiggle it back and forth. What are the consequences of that?

BTW2, I found some gear oil in the case when I pulled the final drive off my main K75 a couple months ago. There is a seal leaking a little but I don't know 1) which one it is 2) whether its fixable without a Bruno-style rebuild 3) whether I would do it even if it were fixable. I'm will pull it again in a couple months to lube so I'll have a better idea of the rate of leakage then. What are the consequences of a gear oil leak in there?

Thanks for any input -- I can't wait to see what the clutch splines look like  :dunno2:

Van

[wmax351]

They are definitely worn, but I think they have some life left in them.


The red crud is old grease, the BMW red stuff. Which partially explains the wear. 70K is not too bad for a driveshaft lubed with the Red #10 grease.


If this is a temporary bike, I'd just ride it. If it goes bad, just buy one off of ebay.


Regarding the leaking FD: It is fixable without a full rebuild. That nut is crazy torqued though, best bet to have a shop do it, unless you can weld together a jig to hold the FD. That being said, mine is leaking, and has been for a while. It's a bruno's rebuild unit too. I switched over to Redline Anti-shock gear oil, which is a bit thicker, and is partially solid(ish). I haven't checked since I switched, but I bet it reduced the leakage. But the leakage isn't too big a deal.

[Motorhobo]

Thanks -- I guess I'm not sure whether I'm going to keep this one or sell it...can anyone venture an approximate percentage value on what's left on those splines? I know they'll go for quite a while if lubed every 6k with GD but if I do choose to sell it it'd be nice to have something to say besides 'quite a while' ...

I know it's probably not possible to gauge that from photos, though.

[pallum]

My original set looked about like yours do. I put another 10k miles on it (lubed twice) and the shape did get worse. The extra space in between spline walls allows the shaft to bang around and will hammer the teeth out eventually. I got a Bruno rebuild once mine looked like this. YMMV

Edit: The radial play is normal  :2thumbup:

[Motorhobo]

Edit: The radial play is normal  :2thumbup:

Wow! Some good news!

The bad news -- I've got a pile of driveline parts all of which need rebuilds and noone's going to give me any money for a Kbike with crappy splines  :musicboohoo:

Oh well. I'll keep it as a spare bike after all.

V

[bocutter Ed]

I'd be tempted to send those to Bruno, swap in the parts from the bike you're rebuilding, then the rebuilt parts can go in your keeper.

[Motorhobo]

Yeah...but I already have an extra FD and DS...so now it's eenie mienie mienie mo to pick which one goes to Bruno. The conundrum is do I put the crappiest one in the extra bike and sell it for dirt, or put a better one in the extra bike to sell for more $$$ ...

I know...too many splines, so little time  :musicboohoo:

[ReneZ]

I'd worry about the splines of the shaft at the FD end. There's not a lot of live left in them.

[Elipten]

Looks heavily worn to me.  Will leave you walking soon.  Most owners will not know or pay to lube the splines, and the same for most dealerships in my experience.  So bikes with 30k miles or more are a risk, so I just figure the Bruno cost in the purchase.  The issue is the time it takes.

[Motorhobo]

Thanks -- I've decided to use my spare DS for this bike and keep this trashed DS for delivery to Bruno -- if I could reach him. Doesn't answer phone or email -- I guess he's pretty popular dude.

I'm going to use this FD though. I think there's a good many miles left on that if lubed with Guard Dog every 5K.

I have heard that it's good to keep the FD and DS matched up when possible -- that is, treat used FD and DS as a matching set. Is even partially true or a complete non-issue?

[Elipten]

Send Bruno an email, he calls back.  Maybe holiday travel?  Not sure about keeping matched but makes sense, as you would think a worn FD would wear new DS quicker.

[Motorhobo]

Talked to him this morning -- $180 for just the DS $800 for the pair. Need to check my credit limit.
V

[Elipten]

Wait to you see the shipping cost in each direction, but I assume you a getting the FD longer spline.

[vintagemilano]

Generally with any spline when it gets worn to knife edge, still full height but just knife edge you then have zero life remaining. Having said that, if you do choose to run it till it breaks, when your splines finally do come to the end of their motive life it won't be some big crashing around catastrophe. The outer spline will spin on the inner spline  but will all be contained.