R1100S Output Shaft Seal Woes

[weaselonastick]

Folks,
I've posted on the Pelican forum, but wanted to make sure I got a Global perspective on my issue.

I've replaced the transmission output shaft seal on my R1100S at least 4 times in the last two years. After the last failure, I was fed up, and completely dismantled the transmission and replaced the output shaft bearings and the seal on the workbench (rather than on the bike like the I've done in the past). I did that a few weeks ago, and the bikes has sat idle since then (not even started). I checked it today... and the seal is leaking. Just to be clear... a new OEM seal was installed 3 weeks ago, and the transmission filled with oil; the transmission has not done a single revolution since then, and transmission oil is leaking around the shaft.

Bike has about 27K miles. 2004 model.

I thought that in each case I was careful with the new seal, making sure to protect it from scoring when sliding it over the output shaft. Particularly with the transmission on the bench.

On some of my original searches to replace the seal I seem to remember two possible causes for failure... a) worn bearings (causing the shaft to wobble) and b) something wrong with the new OEM supplied seals. The location of the seal in relation to the shaft was also critical, but looking at the shaft (out of the transmission), I'm not sure that is a valid point... the shaft is the same diameter from the chamfer behind the splines all the way into the transmission (directly under the seal location).

So I've replaced the output shaft bearings, and used multiple OEM seals.

So I'm at wits end.

I'm looking for any suggestion, no matter how significant or insignificant to solve this issue.

Thanks in advance.
Mike

[Jeff Highland]

A scratch on the shaft?
A seal is only as good as the surface it mates to.

[weaselonastick]

Jeff,
Nothing that can be seen or felt on the shaft. We ran 600 grit wet-dry on the shaft (1-2 light passes) just to make sure.
Mike

[Jeff Highland]

You are sure it's leaking around the shaft not the outside of the seal to the housing?

[weaselonastick]

Absolutely. I can see the oil forming a ring around the shaft, then dripping/running down the seal face to the transmission housing.

[Jeff Highland]

Sorry I can't suggest anything else, good luck

[Jeff Highland]

Unless the shaft for some reason is undersize

[nab 301]

you've probably found this post , viewtopic.php?f=4&t=16772&hilit=output+seal&start=15
Maybe try a seal from a bearing supplier.
Some seal sizes listed at the end of this post
viewtopic.php?t=10343&postdays=0&postorder=asc&start=15

[weaselonastick]

I think I've got it sorted, based on some feedback from the BMWMOA forum.
In every case, I've replaced the seal while the transmission was still on the bike AND driving the seal all the way to the back of the housing (against the bearing within the transmission).
With the trans on the bike, you can't see the oil hole on the shaft.
Driving the seal hard against the bearing puts the seal right over the oil hole.
And that's why the location of the seal in the housing is important, but I believe it's not the best design.
The housing depth is approximately 7.5-8mm, while the seal is 6mm deep. That basically gives a 1.5-2mm tolerance on the location of the seal.
The oil hole on the shaft appears to be about 1-1.5mm from the bearing face.
The seal ring(?) on the seal itself appears to be about 0.5-1mm from the rear of the seal (or 0.5-1mm from the bearing if you drive the seal against it).
So you really don't have much flexibility on the location of the seal. On my bike, the seal must be located flush to the face of the transmission housing, not seated against the bearing.
From what I've read, most people craft some kind of seal driver with a stop, so the the seal only goes a certain distance into the housing.
I don't have a lathe to make the seal driver, so I made a large washer from PVC that sits against the bearing, that you can drive the seal up against and it will stop.
The washer is 40mm OD, 2mm thick and 30mm ID. This still allows oil to come out of the oil hole on the shaft to lubricate the seal, and makes a solid stop for the seal.
I haven't ridden the bike yet, but I did spin the shaft a pile of times... 48 hours later and no leak. I'll report in after I've got the bike back together and done a few miles.

So it appears to be operator error, and not the seal.

Nab301.. I sourced a 25x40x7 seal from a local hydraulics shop and tried it on one of my earlier attempts. The 7mm width moved the seal ring further away from the bearing, but not enough to clear the oil hole IF you seat the seal against the bearing.

Thanks to all who've offered support.

Mike

[weaselonastick]

I was advised that in placing the washer over the bearing, I've likely blocked the oil path back from the seal through the bearing into the gearbox... so I'll be removing the spacer this weekend.