Differential Rear Spline Lubrication Interval

[bicyclenut]

Replaced tires on my RT today and last final drive service was about 10,000 miles ago but I decided to go ahead and do the service rather than wait 2,000 miles since I had wheels off.  It is my understanding it is recommended to be done every 12,000 miles or maybe every year. At my last rear differential service I also inspected the rear U-Joint and lubricated the splines with a recommended Moly-based grease. I also did this again today, but I am wondering if I really need to do this as frequently as I have heard it as a recommendation, but I don't really see this in any maintenance interval information from BMW. Didn't see any issues with driveshaft splines, interior was free of moisture, dirt and seemed to be sufficient grease from last service.  2010 R1200RT

[David.]

This and other recent threads about lubricating the driveshaft splines got me thinking, (dangerous I know).

The driveshaft has two universal joints, one at each end. Both the gearbox output shaft and the final drive unit input shaft are splined.
Have never seen any mention of lubricating the splines at the gearbox end of the shaft.

On early Hexheads, there wasn't a final drive unit oil drain plug. The FD unit needed to be dropped/pivoted to drain the oil.
https://www.youtube.com/watch?v=ymGZjKPXSAQ
Having said that, on my 2007 model, the oil was changed at the 600 miles running-in check. It was filled with "long life" oil and never done again.

Both Camheads and Wetheads have FD unit drain & fill plugs, negating the need to drop the FD unit.

If the FD unit is not dropped/removed for maintenance, why should the splines need lubricating and if they need doing, how about the gearbox end.

My Yamaha XJ650 is 40 years old with over 50,000 miles on the clock. The shaft drive has one UJ at the gearbox end of the splined shaft.
It doesn't get regularly lubricated and hasn't failed yet. Nor has is been a problem to dismantle when removing the swinging arm or FD unit.

[bicyclenut]

I am guessing, but not sure that the transmission output end is more protected from water and intrusion that might cause corrosion or damage to the splines. The FD end has the rubber boot that is subject to damage or water intrusion that will affect the splines on that end. I'd have to look at a diagram or figure out if the trans output side has any sort of a flexible seal that would be more easily damages or it has more of a protected and less vulnerable seal that has less of a likelihood of water, dirt or other intrusion that it does not require regular inspection or service.

[David.]

You could well be right, however, if you do want to lube the transmission output end, have a look at this video,
https://www.youtube.com/watch?v=-ub07EkInVY

We now probably know the real reason why folks don't do it.

[Old-Git]

20k on my bike, and look what I found today. Shaft had seized onto the bevel drive....

[LAF]

And that is why EVERYONE should look at thier splines at least once.
Here is a step by step who I attend his yearly tech meeting of about 60 or so bikes.  I tought and did cam checks on 1200's last year the whole time there.
If you look through this link you will see why you should look at your splines.

https://www.jvbproductions.com/R1200_Wethead_FD.html

[Beagle]

I had to replace the shaft in my old K100RS. It had worn the splines like it had been machined. It was also dry and coated in rust powder. It was only curiosity that made me strip and look at it. I was not aware of these issues.


I noticed my R1200RT has a surplus of white grease around the hinge seal from new.

[LAF]

I had to replace the shaft in my old K100RS. It had worn the splines like it had been machined. It was also dry and coated in rust powder. It was only curiosity that made me strip and look at it. I was not aware of these issues.


I noticed my R1200RT has a surplus of white grease around the hinge seal from new.

That is the sealant that is used to seal those boots  Staburags NBU 30 PTM.  It is pretty pricey around 16 dollars but I bought a 25 Gram jar off of Amazon.  It is really sticky and seals that FD boot to the FD like glue.  Mine even though it was sealed tight and I mean tight it still was more rusted then I would have liked to see at 12K on my 17.5 GS.
I used Honda moly paste on the splines even though this NBU can be used as a lubricant also.  I was advised the Honda will work as good or better and then use the NBU to seal as that is your only defense on water intrusion.  I do not think this needs done more then every 24K.  Mine at 12k was dry and rusted but not anything like some of the pictures in that link I shared.

[Beagle]

I wonder how much condensation plays a part in the corrosion rather than water ingress.

[Beagle]

What about the U/J and splines at gearbox end?

[David.]

This video, https://www.youtube.com/watch?v=-ub07EkInVY shows how to lubricate the UJ splines and the gearbox output shaft on a Camhead.

I imagine it's a similar procedure on a Wethead.

[Beagle]

I am aware of shaft removal instructions.

I wondered why previous owners with the bevel end problem had not mentioned the gearbox end.

[David.]

Possibly because the gearbox end is less vulnerable from exposure to moisture & potential corrosion.

Plus, it looks like a right chew on to lubricate.

[Old-Git]

What about the U/J and splines at gearbox end?

I was sorely tempted to lube at the gearbox end, but some voluntary riding might have been happening so I wanted to get the bike back together soonest. Neither of those things happened but that's another story. I'll have a go this coming winter. BTW I used blue lithium complex marine grease on the rubbers, small tin dead cheap on ebay.

[Beagle]

Possibly because the gearbox end is less vulnerable from exposure to moisture & potential corrosion.

Plus, it looks like a right chew on to lubricate.

Seems only a little more to remove shaft and reassemble both ends with grease.