Final drive noise

The bike: '96 R11RT, 37,000 miles. Two years and 3000 miles ago I put in a new clutch, had the tranny rebuilt by Rubber Chicken, did a spline lube. I've had the bike for nine years and 15,000 miles.

Late last fall I started hearing a sort of rumbling or groaning noise coming from the final drive area. It sounded something like gears with too much backlash or like agricultural flotation tires on pavement. It wasn't loud but I could hear it. Everything seemed to check out ok, everything tight, no grumbly feeling when rotating the tire, no excessive backlash. Today the noise got louder. Still, things feel tight enough. I drained the final drive lube. There was no metal on the magnet. However; the normally clear red Spectro full synthetic 75w/90 was black. I'm wondering if there is a sealed bearing that's not so sealed anymore and contaminating my oil? There is no play at the wheel so I suspect the pinion bearing.

So, my questions to the group: Have I lost a bearing seal? Would that cause the noise?

Thanks in advance.

Firstly:

Is the rear tire correctly inflated?
What condition is it in?

There are no sealed bearings in the FD
Does the FD grumble when you turn the wheel on the centrestand? (now)
If not, refill FD with fresh gear oil and monitor drain magnet closely (every 1000 miles)

Drive shaft?

Re-torque your rear wheel would be the place I would start. Good quality oil in the FD for sure but some oils do turn darker in gear sets by design.

I've got PR2s with about 4000 miles. They're in great shape still. I run 38 psi in the rear. I changed the oil today but haven't been back out for a ride yet. Turning the wheel makes no noise on the center stand. I'm still wondering why the red oil turned black as if there was a moly additive in it. There isn't. I've been using the same oil since I bought the bike. This is the first time it turned dark. I'll try it for a while without the bags. Maybe the noise will be easier to hear.

When I had the driveline apart I found that the driveshaft wasn't perfectly phased. It looked as though the sections had twisted maybe five degrees. The joints were in good shape. Would an out of phase shaft make this kind of noise?

I'll check the wheel bolts tomorrow.

Thanks guys.

GSAddict said:

Firstly:

Is the rear tire correctly inflated?
What condition is it in?

There are no sealed bearings in the FD
Does the FD grumble when you turn the wheel on the centrestand? (now)
If not, refill FD with fresh gear oil and monitor drain magnet closely (every 1000 miles)

Click to expand...

chubbyknuckles said:

When I had the driveline apart I found that the driveshaft wasn't perfectly phased. It looked as though the sections had twisted maybe five degrees. The joints were in good shape. Would an out of phase shaft make this kind of noise?

Click to expand...

No.

Somebody can correct me if I'm wrong but I haven't seen a BMW motorcycle drive shaft with the rubber damper in the center in phase perfectly yet, even new out of the box. They all seem off-kilter a bit and I just assumed that some engineer decided that when under torque, it would return to phase.

But yeah, out of phase can give you some funny noises and some vibration.

dieselyoda said:

But yeah, out of phase can give you some funny noises and some vibration.

Click to expand...

True, if significantly out of phase - like 45 degrees or 90 degrees - not 5 degrees or part of a spline.

For years BMW made no effort to phase shafts at the factory and we would find them every-which-way on initial disassembly. And service manuals for years never mentioned a single word about phasing shafts. As far as I know they still don't but I haven't looked at very many new ones lately. A tech coming back from tech school advised that when questioned the instructors were saying it didn't make any difference.

Now I don't agree for a minute. It does make a difference, and the greater the deflection angle (GS anybody) and the greater amount out of phase, the bigger rotational velocity change through the joints. And thus, the greater stress on the U joints.

What the 2000 factory OE cd says:

Caution:
The universal joints for universal shaft and rear
wheel drive must be installed in the same position.

Rather vague IMO

dieselyoda said:

Somebody can correct me if I'm wrong but I haven't seen a BMW motorcycle drive shaft with the rubber damper in the center in phase perfectly yet, even new out of the box. They all seem off-kilter a bit and I just assumed that some engineer decided that when under torque, it would return to phase.

But yeah, out of phase can five you some funny noises and some vibration.

Click to expand...

Mine was apart recently and we found that the shaft was out of phase from the factory. No one had been in there before as evidenced by the loctite used etc. When putting it back together it was not possible to get it perfectly aligned in phase. You had to choose one spline one side or the other but it wouldn't line up perfectly. I suspect they are all like that.

happy wanderer said:

Mine was apart recently and we found that the shaft was out of phase from the factory. No one had been in there before as evidenced by the loctite used etc. When putting it back together it was not possible to get it perfectly aligned in phase. You had to choose one spline one side or the other but it wouldn't line up perfectly. I suspect they are all like that.

Click to expand...

Tom Cutter has observed that, and he has hypothesized that given the stresses are highest under heavy load, that the rubber absorber in the shaft deforms enough to have the joints in phase when the load is greatest. Interesting thought and maybe correct.

Phasing

I would tend to agree with D.Y. relative to the phasing of the assembly.
That would be pretty clever to have engineered the out of phase condition to return to "spot on" when under loading but that would require of course that the correct spline engagement was choosen on assembly - either direction (and coast would not be all that productive). It would appear however from most posts that BMW was not paying close attention to the assembly when it went together based on how units came apart.

Regardless and having to do with the original symptom of "rumbling or groaning noise" from F.D. area - seems pretty unlikely to have that developing from phasing which would have potential to generate torsionals, and ultimate "U" joint damage etc. Equally if the phasing was changed at time of clutch job 2 years ago seems like you would have heard/felt some symptoms before just last fall if that was the issue.
Perhaps the sound is traveling via driveline from another area (typical of driveline noise to eminate from one point and be heard at another). Hows the tranny doing? Hypoid gear noise tends to change between loaded and coast condition, is that taking place? Could the "black" appearance of your gear oil have come from something non metalic expiring within the assembly?
Just a few more questions to compliment the process.
Good luck.

Originally I was concerned that there was a sealed bearing that could be failing. I couldn't tell from diagrams if any of the bearings were sealed. After some careful inspection and a couple of rides yesterday I'm thinking GSAddict is right about tire being the issue. The PR2 is in good shape but showing some wear after 4000 miles. The half loop at the center of the tread pattern is showing a slight scollop, nothing I would consider unusual. The sound was something that I would notice every time I was out but would forget about when I got home. Until the other day it didn't change so I didn't worry about it. Yesterday I took off the bags and rode the same stretch of brand new pavement I was on for the first time Saturday. The sound got louder at nearly the same spot on the road as before. So, off I went to listen to some tire music. It seems that new concrete makes the tire sing a bit, kinda like an ag tire on pavement. Forty miles an hour on a curve is the loudest combination. Around here new roads means lots of locals starved for entertainment bragging about being the first to drive the new stretch, not kidding. I usually ride the less traveled asphalt or chip-and-sealed roads that everyone is bored with.

The Michelins have been great tires. I never read about anyone reporting any excessive noise coming from them so that wasn't my first thought. Usually problems crop up from something I've messed with. I now wonder if the new model PRs have a little rumble to them?

Thanks for the great info. And yes, I'm aware that it looks as though I was a starved for entertainment local on a new stretch of road.

I have no idea why my oil turned black.