2015 drive shaft phasing

[millsaps2]

"Benchwrencing" is a huge part of the WHY I read these magazines!

LFarling - Changing the angle of the driveline doesn't change the phasing; phasing is totally dependent on the orientation of the U-joints with respect to each other.
(Side note - How "close" you can get depends on how many teeth are available to slot the pieces into; more teeth = closer alignment).

I've said it before but it needs saying again: I have personally witnessed brand-new shafts still in the BMW packaging that were out of phase. It is up to the mechanic working on the bike to look at what he's doing and do it right.

Of all the you tubes I have watched for the drive shaft service I have not seem the mechanic align the shaft on the splines at the gear box output shaft or the rear gear box. You would think if this was critical an index mark would be present for the alignment. If I look at the drive shaft housing on my 2016 R1200 GS the angle of the shaft from the transmission to the drive shaft is larger than the angle at the rear gear box with the bike on the center stand. Maybe the universal joints are put slightly out of phase to correct the angle difference, of course the angles changed slightly with the bike loaded.

 

[pauls1150]

Perhaps there is a misunderstanding here...
Driveshaft phasing is the relationship of the Front yoke of the driveshaft to the Rear yoke of the drive shaft - they should be in the same plane.
Here are a couple of pictures to illustrate:



Properly "phased", it is the YOKES on the shaft that "aim" the same way.

The output shaft of the gearbox, and the input of the rear bevel drive, are not part of this equation.

As the suspension travels, of course the angle of the driveshaft housing will change - and THAT IS WHY there are two U joints, one at each end, specifically to allow this movement.
A knowledgeable experienced mechanic doesn't need index marks for this, as there are exactly two points in the rotation of each side where they'll align per the "Correct" pictures above; those being the first obvious alignment and the second being 180 degrees "away from" the first point.

Consider the "circle" of the mates as having 360 degrees of circumference. If there are ten teeth (splines) on the shaft, you have ten possible alignment points, each being 36 degrees away from the next. But only two will be correct. Twenty teeth, and you have twice as many places to attempt alignment, and they're 18 degrees apart....Closer! More splines can get you closer at the risk of weakening the part due to thinner teeth. But the people who design and manufacture driveshafts know this, so they consider all of the unions along the driveline path during design, so as to create a product that won't vibrate a little or eventually self-destruct.

The square driveshaft is used as an example to "magnify" the wrong way; this shaft would only have two correct places plus two incorrect places for the yokes to line up.

 

[millsaps2]

Perhaps there is a misunderstanding here...
Driveshaft phasing is the relationship of the Front yoke of the driveshaft to the Rear yoke of the drive shaft - they should be in the same plane.
Here are a couple of pictures to illustrate:
View attachment 91195

View attachment 91196
Properly "phased", it is the YOKES on the shaft that "aim" the same way.

The output shaft of the gearbox, and the input of the rear bevel drive, are not part of this equation.

As the suspension travels, of course the angle of the driveshaft housing will change - and THAT IS WHY there are two U joints, one at each end, specifically to allow this movement.
A knowledgeable experienced mechanic doesn't need index marks for this, as there are exactly two points in the rotation of each side where they'll align per the "Correct" pictures above; those being the first obvious alignment and the second being 180 degrees "away from" the first point.

Consider the "circle" of the mates as having 360 degrees of circumference. If there are ten teeth (splines) on the shaft, you have ten possible alignment points, each being 36 degrees away from the next. But only two will be correct. Twenty teeth, and you have twice as many places to attempt alignment, and they're 18 degrees apart....Closer! More splines can get you closer at the risk of weakening the part due to thinner teeth. But the people who design and manufacture driveshafts know this, so they consider all of the unions along the driveline path during design, so as to create a product that won't vibrate a little or eventually self-destruct.

The square driveshaft is used as an example to "magnify" the wrong way; this shaft would only have two correct places plus two incorrect places for the yokes to line up.

But how do you align the standard BMW shaft which we know is out of phase from the factory?

 

[pglaves]

But how do you align the standard BMW shaft which we know is out of phase from the factory?

If it is a two-piece shaft you just do it. If it is a one-piece shaft you just install it, do three curtsies, bows, hail Mary's, or chants of your choice and hope. As I noted in my earlier post about my Benchwrenching columns, BMW does not seem to pay much attention to this issue at the engineering level, for whatever reason each of us might imagine, As I said earlier, the manuals did not address the issue on the Oilheads at all. I might surmise that the engineers didn't believe the stresses were enough to be an issue but common U joint failures, especially on the GS models soon proved that to be a fallacy. I stopped trying to understand engineers (my father was a mechanical and agricultural engineer) a long time ago at about age 14. I certainly do not understand many things BMW does or has done. Please just try to explain the R100GS sidestand or R1100 left cam chain tensioners.

 

[52184]

Sounds like burnt offerings may be our last hope…



Best,
DeVern

 

[pglaves]

Sounds like burnt offerings may be our last hope…



Best,
DeVern

Probably.

 

[LFarling]

I purchased the EI drive shaft from Ted Porter several years ago. I just looked at his website and the airhead version is still shown (for $700).

https://www.beemershop.com/product/...00r-r80gs-paralever-models-generation-ii.html

View attachment 91193

Yes but he had LC shafts for a bit and then needed to pull them I think.

I know I was disappointed as it would be the one I would buy. And I would have bought a rebuild kit at the same time to have on the shelf. Man to have a serviceable DS that can be rebuilt is all that and a bag of chips, with salsa too.

The DS seems to be the weak link on these bikes. It could be worse like shocks, or final drives, cams and followers, stator, or brakes

 

[LFarling]

"Benchwrencing" is a huge part of the WHY I read these magazines!

LFarling - Changing the angle of the driveline doesn't change the phasing; phasing is totally dependent on the orientation of the U-joints with respect to each other.
(Side note - How "close" you can get depends on how many teeth are available to slot the pieces into; more teeth = closer alignment).

I've said it before but it needs saying again: I have personally witnessed brand-new shafts still in the BMW packaging that were out of phase. It is up to the mechanic working on the bike to look at what he's doing and do it right.

I understand phasing, as I said I took care of a 07 LT for a few years.

What I meant to say is maybe the phasing is off to offset some angle or allow slop for whatever reason. I mean in gear the rear wheel has front and rear movement. Maybe the few degrees that BMW one is off for some reason.

Either that or to them it just does not matter.

It seems the "good" ones fail in the 60 to 80K range so to me, for a non serviceable item, I would replace in that range.

I still do not understand as DS on trucks and cars last forever and exposed to much more of the environment, yet these are falling apart at all kinds of mileage?

 

[BBrowning]

Good discussion.. Being an automotive guy when I pulled the driveshaft for inspection I thought "this is just wrong". But I have to assume, you know what that means, LOL. That BMW knows what they are doing.. I am not up to free replacement yet but close.. Still I think I will order a shaft to keep on hand 'just in case'.. Where I go on trips, dealers tend to be thousands of miles away so I have to deal with things as they happen.
The shaft out of my bike.. 2018 R1200GSA To me This is just wrong.

 

[pauls1150]

Agreed; if you can separate the halves, then it appears that the "right" half needs to be moved one tooth counterclockwise with respect to the "left" half ... or maybe, with the number of teeth on the shafts, that could actually be "as close as it's gonna get".

 

[Omega Man]

Maybe it is the short shaft on the BMW bikes?

Why is driveshaft phasing important?
Driveshaft Phasing & Its Importance - Managed Mobile, Inc.
Driveshaft phasing is the process of aligning the driveshaft, U-joints, and slip yoke to balance and prevent unwanted vibration from the vehicle's driveline system. In some cases, there are two or even three shafts that need to be aligned properly to ensure that vibrations are not transmitted throughout the vehicle.

I have done U-Joints in lots of drive/prop shafts and jus put them back the way I found them with index (chisel or punch) marks.

OM

 

[pauls1150]

Another case for some moly on the splines!

 

[jimbem]

The bike in question is 2015 that had 224,000 on it when the stator went bad . I has less than 1000 more miles since the stator replacement job.
The original drive shaft went bad at 168,000. It was replaced with a used shaft from a totaled 2015 RT-P with 22,000 miles on it.The bike ran as smooth with the replacement shaft as it did with the original until after the stator replacement.
I watched the videos and from what I got from them improper shaft phasing should not be my problem the u-joints are welded onto the shaft and can't be installed out of phase.
I have not ridden that bike since late fall as it stays in Illinois for the winter.But the way I remember it the bike only vibrated bad under load at speed. Not while coasting or at more normal cruising speeds. When we get back north in mid May I will take it back to the dealer did the stator work. But in the mean time I am open to suggestions as to what may be the cause of new vibration. It would be nice to be able point them in the right direction to fixing it . Thanks

i realized today that I never posted what the final diagnose was on my old RT. IT wasn't the stator or the driveshaft. The right cylinder is weak with lower compression than the left cylinder.
Before I took it back to the dealer that installed the stator I checked and adjusted the valve clearances , checked the cam timing, installed new spark plugs and air filter. The bike still felt like one cylinder wasn't firing as strong as the other so I used my laser thermometer on the exhaust pipes . The right cylinder was about 50 degrees cooler the the left. Then I swapted the ignition coils left to right and checked the exhaust temperatures again. With my fingers crossed ! My fears were confirmed , the right cylinder was still cooler . I took the bike back to the dealer and did a leak down test and compression check and said the rigth cyclinder is indeed weak. He wrote the numbers from the tests on paper but that paper is in Florida and I'm not right now.
I am very disappointed . This bike ran great before the stator went bad and had to be replaced. If I felt a weak cylinder theres no way I would have spent all that money on the stator job. I can't say it was anything the dealer did. I am afraid it was me . About 2 weeks before the stator went bad i was enjoying the bike on an almost deserted interstate and made the bad decision to see how fast the bike would still go. I shut down at 8 miles per hour less than what the top speed was years ago. I shut down because it was clear the bike had alot left in it and I didn't want to abuse the bike but apparently I already had.
So feel bad because after having put 225k on that bike I was quite attached to it. It was like an old friend that I hurt. I still have the bike and at this point have no intention of getting rid of it. I use it to run errands close to home or if i need to go somewhere while it's raining or snowing lightly. And yesterday it occurred to me that I can use it for practicing slow speed maneuvers.

 

[BBrowning]

Maybe it is the short shaft on the BMW bikes?

Why is driveshaft phasing important?
Driveshaft Phasing & Its Importance - Managed Mobile, Inc.
Driveshaft phasing is the process of aligning the driveshaft, U-joints, and slip yoke to balance and prevent unwanted vibration from the vehicle's driveline system. In some cases, there are two or even three shafts that need to be aligned properly to ensure that vibrations are not transmitted throughout the vehicle.

I have done U-Joints in lots of drive/prop shafts and jus put them back the way I found them with index (chisel or punch) marks.

OM

It would be nice if one could correct the phasing of these shafts but sadly no.. They are bonded together with the Elastomer.. My first thought was it was twisting but after thinking about it it would have had to twist 270 degrees and I doubt that it would do that with out complete failure.. Anyways. it appears as if BMW doesn't care where they end up or they have some hidden reason for having them out of phase..
When I built the Racecar I fussed over the driveshaft angles. Being a real short driveshaft I placed things so I had less than 3 degrees angulation and kept it the same front to rear.. Having a 3 link in the back I had to worry about pinion angle and if I changed that a lot with my upper link suspension adjustments I had to also compensate with the angle at the transmission end.. Maybe I did all that fussing for naught. LOL

 

[Omega Man]

Maybe I did all that fussing for naught. LOL

Not if it worked!

OM