Spline replacement?

[know_fear]

I recently took a K75 final drive unit to a shop that specializes in driveline repairs to get a repair estimate. I thought they could cut the trashed splines off the pinion shaft and weld on a new stub to match the new driveshaft. I was quite surprised to hear that it isn't possible. He said that it would not be exactly straight and wouldn't last long. I was prepared to find it more expensive than a good used one but even those will dry up eventually.
Has anyone else tried to have a repair such as this done?

In 2011 I sent my '85 final drive to Bruno's Machine in Ontario. The originals lasted 166,000 Kms but were in need of attention. I believe the early splines were 16 tooth but now my '85 has the newer style 20 tooth so I know there is a process to replace the splines and have them straight. Bruno has unfortunately closed shop.

 I'll look for another machine shop that feels confident of a complete repair. It may be that the first place didn't want to deal with a unique setup.
Thoughts?

[Laitch]

The pinion gear and crown gear are matched pair so I believe you correct in thinking that the shop was unwilling to commit time to making a unique, untried setup. Keep up the hunt. There might be some folks who will take up the challenge if you can make it worthwhile for them. It's also possible you might come across a final drive in much better condition if you hunt persistently.

[The Mighty Gryphon]

Am I missing something here?  MaxBMW shows p/n 01    33 12 1 457 062 CROWNGEAR SET for $524.  That includes the pinion gear with new splines.  Yes, you will need new seals and probably some shims, but you'll have a new final drive when finished.

[Laitch]

Am I missing something here?

I don't believe so. Maybe Max does have some of those on the shelves but, as Max cautions, the fiche doesn't necessarily reflect its inventory; it's just a vessel of Hope sometimes.    Let us know, know_fear.

[know_fear]

Plus another 3 or 4 hundred $ for bearings if they have not survived the disassembly.
I think I should check other machine shops.

[Laitch]

This might be the time to consider converting the moto to a paralever drive, as has been done with good results by a few members here. 

[Past-my-Prime]

Well I had the shittiest drive shaft splines and found a replacement shaft / FD combo from a very nice member on this site (thanks Volador!) after which I'm back in a good place (and I lube my splines with Honda Moly every time I do an oil change).

Maybe you'll find a decent shape set from a brick breaker?

[know_fear]

That will be the best course of action PmP.
Once I have a good final drive I'll take the worn one apart and see what can be done, if anything.
What did you do with your old one?

[Past-my-Prime]

Still have the original DS and FD which I'm considering sending for renewal of the splines. But right now it's with my spare parts and not much good to me until I fix.

[know_fear]

Do you have a place in mind for the repairs?
It would be good to get the opinion of another shop as to what the cost would be.

[Past-my-Prime]

Here's an email I got back which scared me a bit, and is why I went with a good quality used driveshaft / final drive. Obviously this service is the best way to do it but seemed VERY expensive. And note that this was three years ago, so it's probably only gone up in cost!

There used to be a place I think in Toronto, Brunos, but they are no longer in business as far as I know. Someone else will probably have other ideas for you as well.

Mind you, my driveshaft was completely toast, and my final drive teeth weren't that much better!

So I don't know what I'll do with the old one. For now, I'm good with my replacement.

-------------------
email from Hansen's:

On Sep 10, 2019, at 17:17, Craig Hansen <craig@hansensmc.com> wrote:

<image001.jpg>
Hi Michael,
 
Thanks for the inquiry about repairing the Pinion Drive Spline on your BMW K Model, which is a service we do by mail.  You probably don’t have the factory tools to disassemble the final drive so in your case I would send the complete final drive.  Because we can't see your final drive it is difficult to give you an exact estimate, depending on mileage & condition there are many variables.  If you send the complete rear end the cost is $759.20 to $1,374.93.  If you send the Pinion Gear only, the repair is $240.  I explain below the different combinations and what we normally see.
 
First, we disassemble & inspect the final drive gears and bearings.  If bearings & gears are OK, we check the backlash in the gears & adjust as needed.  Then we check the preload on the ring gear bearings & adjust with shims as needed.  Finally, we replace the pinion and housing cover seals then assemble.  If the rear end has more than 50,000 miles, we recommend replacing the ring gear bearings.
When the Pinion Gear is out, we rebuild the splines.  If you already have the Pinion Gear removed, you can just send it for repair with a list of parts you that you need.  Pinion removed, additional $240.
 
You also need to replace the drive shaft, and it can't be economically rebuilt it.  To help cost of replacing the drive shaft we give 10% off a new BMW drive shaft with our rear end repair.  BMW $374.18, with repair add $336.76.
 
Freight and insurance are additional.  Our turnaround time during the Summer months is 3 to 4 weeks for a complete repair, and 2 to 3 weeks during the Winter.  If you only send the Pinion Gear turnaround time is 2 weeks.  Turnaround time doesn't include shipping, so you need to allow an additional week or two to your plans.
 
If you’re going to send your final drive, please notify me before shipping, so I can schedule an appointment.  Make sure you drain the oil, and when packaging for shipment I suggest double boxing the rear end for protection.  I also suggest you insure the final drive for $1500 in case it is lost in shipment.
 
If you are not sure how worn the splines are, you can email me a picture of your splines & I can advise you on the amount of wear you have.  If you have any other questions, please let me know.
 
---
Craig Hansen
Owner Hansen’s MC LLC
3598 S Pacific Hwy
Medford, OR  97501
541-535-3342
Craig@HansensMc.com
www.HansensMc.com
<image002.png>
 
---

[Past-my-Prime]

https://www.hansensmc.com/--spline-repair 

[know_fear]

Thank you sir! That's way more info than I was expecting but a little discouraging all the same.
I could probably have a local BMW dealer disassemble the drive and send just the pinion down.
There are only 25,000 kms on that rear end.

[Motorhobo]

https://kpartsholland.com/products/k75-k100-rebuild-driveshaft-20-tooth
They rebuild driveshafts, but don't do the FD pinion gear.

https://www.motobins.co.uk/
They rebuild driveshafts, but don't do the FD pinion gear, and also just sell the spline section and let you find someone to weld it on. Or they weld it for you for £119.00 plus shipping, if you're in the UK...if not, maybe you could find someone on this site to handle the shipping angle for you.

IMO it's cheaper to use a worn pinion gear with a rebuilt driveshaft, keep them lubed as best as you can and ride it till it the driveshaft dies than to do the whole pinion gear rebuild. Even with a worn pinion gear you'll get 20k miles out of the driveshaft, which would give you enough time to do rebuild your final drive with a new pinion gear yourself. Or find a decent used FD so you have something to ride while your FD/DS pair is being rebuilt.

The above info is from this link on BMWMOA.

https://forums.bmwmoa.org/showthread.php?91472-2018-%E2%80%93-The-Current-State-of-K75-K100-Driveshaft-and-Final-Drive-Splines-Repair

Both the kpartsholland.com and motobins.co.uk sites are still advertising this service, so it looks like it might be an option for you, all you need is a f*cked driveshaft to send away. They should be dirt cheap. A lot of folks have dead driveshafts lying around...I know I do.

I'd also like to say that finding a matched FD/DS pair is becoming like the Holy Grail with machines this old. If you don't have lots of $$$ to throw at it and lots of time to wait on the pro rebuild of existing parts, unmatched parts are going be become more and more 'acceptable' practice.

[triplek]

At these prices it might make sense to buy a low mileage K for around $1500 and just pull out the drive train.  ;)

[know_fear]

I took a chance and bought a used final drive through Ebay. It has not arrived yet but the photos of the splines look good.
I also have the female end to be welded to the driveshaft as sold by Motobins.
I will report on progress as it develops. Fingers crossed.

[know_fear]

An update on my spline situation.
The final drive I bought through eBay turned out to be great! The splines look like new.
The brake pads that were with it were contaminated with oil but the internals feel fine based on a short ride.
I will repair the driveshaft this winter with a new female spline stub. With luck and lubrication the bike should
be good for many miles. In the meantime I will run the old pair without straying too far from home.
 Thank you to all who chimed in with info and advice.