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Preventing failure in the rear drive R1100RT 1999


Haagh

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Referring to “Major Power train Failure Survey”, updated: 5/15/2007, it has placed, as I see it, my 1999 R1100RT – 24.000 km - in the group of 1999’er with possible “scientific” failures in the rear drive, and now my attention has been drawn to this drive.

At 75 km/h (~ 45 miles/h) and 90 km/h (~ 55 miles/h) there comes a form of repeating shrilling noise from the RD. Until now I have taken it as a form of acoustic resonance in the pinion.

After a longer drive (> 50 km) the RD has max 45 oC (good hand warm) at the surface. In neutral there is no noise when turning the wheel, and there is no worth mentioning “slip” in the pinion.

For 2 weeks I changed to RL Shockproof 75W/250 in the trans, and at the same time I changed the oil in the RD – 3.000 km since last change at the BMW service. The now drained oil was somewhat silvery, but only a little of metallic sludge on the magnetic tap. The new oil was Red Line 75W/90 with LS additioned – characteristic hypoidoil API CLASS GL-5/GL-6.

As I don’t know how a prelude to a failure in the RD takes place, I would be interested to have some replays of how it happens – and starts.

Would it be possible to make some prevents against a failure in the RD, or is it “built-in” in this model of the year and only waits until the right circumstance takes place.

Finally, is my choice of oil to the RD in this subject optimal – and could a more frequent oil change be the right preventing action?

 

Kurt

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Would it be possible to make some prevents against a failure in the RD, or is it “built-in” in this model of the year and only waits until the right circumstance takes place.

Finally, is my choice of oil to the RD in this subject optimal – and could a more frequent oil change be the right preventing action?

 

Kurt

 

 

Kurt,

Sounds to me that your FD is acting normally. My thinking regarding possible mechanical break downs, in the absence of clear "impending doom" signals, is to enjoy the ride.

Use of appropriate gear oil (your selection meets this criterion imo) and factory recommended change intervals is the only treatment that I'm aware of.

Best of luck from Wooster, practitioner of "don't worry be happy"

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Stan Walker

Every week I make a 360 degree check of the tire looking for nails, rock, cuts, etc. I also check the tire pressure.

 

While I'm down there I grab the wheel top and bottom (also side to side) and try to rock it to see if there is any play. I also spin it and feel for any rough spots. Finally I glance at the crown gear seal to see if it is leaking. All of this takes about 30 seconds.

 

Other than that I change oil every year or two using Mobil 1 75W-140 and just ride.

 

Stan

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Referring to “Major Power train Failure Survey”, updated: 5/15/2007, it has placed, as I see it, my 1999 R1100RT – 24.000 km - in the group of 1999’er with possible “scientific” failures in the rear drive, and now my attention has been drawn to this drive.

At 75 km/h (~ 45 miles/h) and 90 km/h (~ 55 miles/h) there comes a form of repeating shrilling noise from the RD. Until now I have taken it as a form of acoustic resonance in the pinion.

After a longer drive (> 50 km) the RD has max 45 oC (good hand warm) at the surface. In neutral there is no noise when turning the wheel, and there is no worth mentioning “slip” in the pinion.

For 2 weeks I changed to RL Shockproof 75W/250 in the trans, and at the same time I changed the oil in the RD – 3.000 km since last change at the BMW service. The now drained oil was somewhat silvery, but only a little of metallic sludge on the magnetic tap. The new oil was Red Line 75W/90 with LS additioned – characteristic hypoidoil API CLASS GL-5/GL-6.

As I don’t know how a prelude to a failure in the RD takes place, I would be interested to have some replays of how it happens – and starts.

Would it be possible to make some prevents against a failure in the RD, or is it “built-in” in this model of the year and only waits until the right circumstance takes place.

Finally, is my choice of oil to the RD in this subject optimal – and could a more frequent oil change be the right preventing action?

 

Kurt

 

Kurt, on most gear drive systems being a car, truck, or motorcycle there are usually a few periods of gear ringing, moan, or other harmonic resonance set up by the gear teeth contact.. If that resonance happens to fall on the resonant frequency of a vehicle part, housing, panel, or shaft it can set off an audible you can hear.. That shrilling noise you hear might be just a normal tooth contact resonance or could be the precursor to something else.. If that tooth contact resonance happen to fall near but not on a similar noise frequency you will also get a beating sound as the two cross over each other then apart again..

 

The large ball bearing seems to be the major failure point in the BMW final drive & in most instances a bearing starting to fail can be heard at low speed or high loading well before heard at higher rotational speeds.. BMW’s final drive design is a bit mystifying to me as you usually don’t spec out a ball type bearing to oppose the axial loading of an opposing tapered roller bearing especially when you add in additional thrust loads of the ring & pinion separation forces.. The ball bearing is a deep groove but still a puzzling design to me..

 

As far as predicting when a failure is about to occur? In most cases a bearing will get noisier as it nears failure & I am sure the BMW final drive deep groove bearing will change it’s noise signature as it nears total failure,, problem is: on a motorcycle there is also tire noise, other gear noise, engine mechanical noise, wind noise, & general ambient noise that probably covers most of the change in bearing noise.. Possibly riding the bike with a known good final drive bearing then listening to the final drive housing with a mechanics stethoscope while riding will give some idea of what a good bearing sounds like, then occasionally re-listening with a stethoscope again at different mileage intervals will allow detection well before a full bearing failure leaves you stranded somewhere far from home.. In my case I just change the final drive gear oil at every engine oil change (doesn’t hold much & is easy to do) .. I pay particular attention to the drain plug magnet looking for SHINY metal particles (the dull gray particles are normal).. I then strain the gear oil through a coffee filer (takes some time to strain it) looking for other little messengers of death.. Whether or not that will allow me to find or predict a final drive failure before it happens remains to be seen though..

 

Twisty

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Twisty, you sound very well informed on the rear end lmao.gif

Seriously though, if I grab the wheel top and bottom, I can get no discernable play, but if i grab it by the sides, I can detect some clunking - not much but its there.

Matter of fact, it is very hard to tell where the play actually is, but if i had to guess, it would be under the boot of the driveshaft or maybe the pivot bolt area.

How serious is this?

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Twisty, you sound very well informed on the rear end lmao.gif

Seriously though, if I grab the wheel top and bottom, I can get no discernable play, but if i grab it by the sides, I can detect some clunking - not much but its there.

Matter of fact, it is very hard to tell where the play actually is, but if i had to guess, it would be under the boot of the driveshaft or maybe the pivot bolt area.

How serious is this?

 

That sounds more like your rear bushings are wearing not the final drive internals.. There was a very good discussion on this a couple of days ago so look back a few days.. Lots of ideas & adjustment recomendations..

 

Baiscally if you hold a finger between the rear brake rotor & caliper bracket then wiggle the wheel you can easily tell if your problem is internal (will move finger) or external (rotor doesn't move in relation to the rear housing)

 

Twisty

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