Final Drive - 1999 LT with 57,000 miles - BMW Luxury Touring Community
 
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post #1 of 5 Old May 17th, 2012, 6:49 pm Thread Starter
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Final Drive - 1999 LT with 57,000 miles

Another FD data point.
Here is why you should not just replace the seal when a FD is leaking oil at the wheel hub:

Owner stated: "...1999 LT with 57,000 miles needs rebuilt as it is leaking oil..."

No history of metal flakes on the drain plug or in the FD lube. The inside of the drive was quite clean inspite of the outside being corroded from exposure to the elements.

With the crownwheel bearing in hand, it felt smooth, like a new bearing. No outward signs of damage or roughness on rotation as is felt when the races or balls are pitted.

After cutting the outer race off the bearing to better inspect the grooves at first glance everything looks fine. No pitting anywhere:


But on further inspection of the outer race groove it can be determined that there is a very sharp edge to the groove around a large portion of the circumference of the groove. My test for this is to scrape the back of a finger nail across the edge of the groove. In some areas the edge of the groove is very sharp and shaves the nail:



In other areas the edge of the groove is smooth:


I imagine that if I had an instrument that would profile the groove, it would show that the groove is wallowed out. This wallowing out of the groove causes a very slight wobble to the wheel resulting in leak at the seal.

I have posted this finding before. I post again here to inform the owner of the FD of my findings and for the edification of everyone else who might experience lube weeping at the wheel hub.
Conclusion: weeping of lube at the wheel hub, even in the absence of other findings such as metal flakes in the lube, most likely reflects an underlying bearing problem and just replacing the seal will not correct the problem.
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post #2 of 5 Old May 17th, 2012, 7:13 pm
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Re: Final Drive - 1999 LT with 57,000 miles

Curtis, it's always good to catch 1 "just in the nick of time", as this 1 shows, very early stages of bearing failure. I've been talking with my VA technician at work, we may do some testing using Vibration Analysis to determine the health of the bearings and gear mesh. It may be worhwhile making a test rig to drive the FD unit a a constant speed. It could be a nice little research project for an apprentice in our workshop. I'll see.

Dennis
1987 Yamaha TY250R
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post #3 of 5 Old May 17th, 2012, 7:21 pm Thread Starter
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Re: Final Drive - 1999 LT with 57,000 miles

Quote:
Originally Posted by K100Dennis
Curtis, it's always good to catch 1 "just in the nick of time", as this 1 shows, very early stages of bearing failure. I've been talking with my VA technician at work, we may do some testing using Vibration Analysis to determine the health of the bearings and gear mesh. It may be worhwhile making a test rig to drive the FD unit a a constant speed. It could be a nice little research project for an apprentice in our workshop. I'll see.
Dennis,

Thanks for posting.
Any observations by folks with experience and training would be appreciated.
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post #4 of 5 Old May 19th, 2012, 12:51 am
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Re: Final Drive - 1999 LT with 57,000 miles

The owner only saw normal fuzz on the drain magnet when doing the annual oil change of the rear and gear box. When draining before shipment there was a lot of fuzz but no flakes.
I purchased this bike from a gentleman in Cumberland Md. who was the second owner with only 10,000 miles on it. The first owner bought it at Hermys BMW in Port Clinton Pa.

A smart owner would have realize that it was his oil and not road dirt on his trailer. But he was having to much fun on his three day trip with his Wing buddies. We left central Pa. and rode over to the Delaware Water Gap and followed the river up into NY. ending up at Ithaca. We then visited the falls in the area and rode around the lake. On Monday we rode over to Corning and came back down Route 15. We had great weather and a good time.
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post #5 of 5 Old May 19th, 2012, 10:11 am
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Re: Final Drive - 1999 LT with 57,000 miles

Two points -

1) Who is the apparent bearing manufacturer ( I think they sometimes trade manufacturing and distribution between themselves so this may not be really valid)?

2) Is there any chance one of the races isn't fully heat treated - i. e. can you touch it with a file?

Weird!
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