Moly lube for spline shafts?

OldCamper said:

Why should these splines ever need to be re-lubed at all?
Just about every manual transmission car or truck ever made has similar splines in similar places and they never need maintenance.
Time for a design change maybe?

Click to expand...

Excellent question that BMW has never answered. The history is interesting though. Spline lubrication was something of an afterthought in the 1970s. But in the early 1980s there started to ba a bunch of failures. BMW then advised that the splines needed to be cleaned and re-lubricated once a year or every 12,000 miles. Eventually there was speculation that there was a big bad batch of input shafts. BMW wasn't saying. If you look at BMW maintenance schedules for Oilheads, for example, you will not find clutch hub spline lubrication scheduled. But one ignores it at their peril because lots of splines have failed. There are lots of theories as to why.

Some are convinced that a lateral misalignment of the centerlines of the engine output shaft and transmission input shaft is the cause. Some see an angular misalignment as the cause. These were established as the causes of some failures on K75 and K100 bikes, when replacing the auxiliary case (bellhousing) cured the problem.

There is speculation that the power pulses from the large twin engines cause fretting corrosion when the pulses from a four, six, or eight cylinder engine would be much less.

But the bottom line is that they need to be cleaned and lubricated because if you don't do it they fail.

I recall that in the mid or late '80's BMW went to electroless nickel plating (or similar process) on the shafts, ostensibly as a fix to the problem. Never saw any follow up on this.

All I can say I know a lot of BMW's that never had there splines lube since new from when they first say the splines needed to be lube. I haven't seen one with a problem yet. By all means I not saying not to lube them. I not sure but don't know if
the K1200 LT's require that service. maybe some one does let me know.

k1200lt00 said:

All I can say I know a lot of BMW's that never had there splines lube since new from when they first say the splines needed to be lube. I haven't seen one with a problem yet. By all means I not saying not to lube them. I not sure but don't know if
the K1200 LT's require that service. maybe some one does let me know.

Click to expand...

The K1200LT bikes are not as notorious for spline failure as are the Oilheads. I have a theory as to why but it is only speculative. One of the attributes of a good spline lube is that it needs to cushion the splines to prevent what is known as fretting corrosion. You can detect fretting corrosion when you find rust on the metal underneath the lubricant still in place.

The power pulses from a twin cylinder engine, each 550cc or more, and the power pulses from a four cylinder engine, each 300cc are distinctly different. Even the human body several feet away (at the handlebars) can feel the difference. I think the likelihood of fretting corrosion and other spline damage is much less on a four cylinder bike than on an equal displacement twin.

PGlaves said:

There is speculation that the power pulses from the large twin engines cause fretting corrosion when the pulses from a four, six, or eight cylinder engine would be much less.

Click to expand...

I'm 100% sure the twins are much more torsionally active than engines with more cylinders.

Look up Torsional Vibration. Torsionals are produced by every/any internal combustion engine; some better, some worse but they are still present. Usually less torsional magnitudes at high rpms and much higher magnitudes at low rpms/idling. It's a huge problem in the diesel engine powered marine industry. Torsional input couplings manufacturers try to mitigate the torsional activity in the propulsion system but these flexible couplings can only reduce most of the torsional vibrations within a set engine rpm range.

I have no doubt torsional vibrations contribute to the wear our splined shafts. We don't have the luxury of a torque converter to absorb the torsionals coming from the engine like a car or truck.

I see no recommendation to lube splines in my RTW DVD

Why aren't I seeing any reference in scheduled maintenance or on the DVD for lubing splines? I mean it makes some sense for sure but it puzzles me why it's not mentioned in the support documentation. But from what I've read here about rusted splines it seems like it's a non issue especially if your riding in dry weather mostly in a lower humidity area. If I had to replace the drive shaft/u-joints I would definitely do it then, but not sure why if no other need to break the boots.

ncpbmw1953 said:

But from what I've read here about rusted splines it seems like it's a non issue especially if your riding in dry weather mostly in a lower humidity area.

Click to expand...

1. Rust isn't necessarily a product of moisture.

2. Your RT-W has a wet clutch and a different gearbox layout than the bikes that are being referred to in this thread.

ncpbmw1953 said:

Why aren't I seeing any reference in scheduled maintenance or on the DVD for lubing splines? I mean it makes some sense for sure but it puzzles me why it's not mentioned in the support documentation. But from what I've read here about rusted splines it seems like it's a non issue especially if your riding in dry weather mostly in a lower humidity area. If I had to replace the drive shaft/u-joints I would definitely do it then, but not sure why if no other need to break the boots.

Click to expand...

The BMW manual calls for assembly lube on the splines, which makes connecting the shaft easier. It's clear from the many reports of completely dry splines that BMW skips the lube in the factory, but these splines do not show signs of wear. Corrosion, yes, but no signs of sliding wear. If the lube was needed to ease sliding motions of the splines we would be seeing many reports of damaged or even seized splines.

When BMW designed the Paralever rear suspension they eliminated the need for the driveshaft to extend with suspension movement.
"The paralever kinematics is designed so that no length change occurs, meaning no shift piece is necessary. "

I think some of the internet emphasis on spline lubrication is a carry-over from the Monolever era when the splines did slide quite a lot with every suspension movement.

I have to drop my final drive to drain it for oil changes, but I seldom actually add lube to the already-lubricated splines. If I were doing maintenance on a newer road bike, I'd drop the FD once to lube the splines for corrosion protection and then forget about them. A GS subjected to water crossings would be dried out and re-lubed on a frequent basis.

BC1100S said:

1. Rust isn't necessarily a product of moisture.

2. Your RT-W has a wet clutch and a different gearbox layout than the bikes that are being referred to in this thread.

Click to expand...

Thanks for that I appreciate it. I'll remain duly relaxed about it then. You definitely need moisture to form rust, but there can be sufficient moisture in the air I think is what you are saying, especially in BC ;o)

ncpbmw1953 said:

.... but there can be sufficient moisture in the air I think is what you are saying, especially in BC ;o)

Click to expand...

It does tend to be "kind of damp" here for 3 months of the year.

Look up the term "fretting corrosion". Then think about a dry un-lubricated spline shaft. Report back.

And when fretting attacks our beloved steering head bearings, the failure mode is known as "false brinelling". And no, I am not suggesting moly grease for bearings.

Omega Man said:

Just for the halibut, I would put some on a 3/4” bolt and nut and set it aside. Every now and then you can run the nut up and down the threads allowing you to check it and see how the mixture is “holding up” due to age.
Let us know if you can.
OM

Click to expand...

Hasn't been a "LONG" time but it has been 5 months already.... the paste on the bolt and nut look and feel the same as when I applied it. The paste has not dried out as far as I can tell and the nut spins easily on the bolt; of course allowing for the "sticktion" of the paste.

This winter I'll drop the final drive and inspect the splines and report back.

craigjv4 said:

Hasn't been a "LONG" time but it has been 5 months already.... the paste on the bolt and nut look and feel the same as when I applied it. The paste has not dried out as far as I can tell and the nut spins easily on the bolt; of course allowing for the "sticktion" of the paste.

This winter I'll drop the final drive and inspect the splines and report back.

Click to expand...

OM