A transmission question - BMW Luxury Touring Community
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post #1 of 2 Old May 19th, 2015, 8:10 am Thread Starter
Join Date: Mar 2013
Location: Wesley Chapel, fl, USA
Posts: 68
A transmission question

These questions / comments are based on an experience I had working on a '98 1200 rs, but mechanically the bike is almost the same as my 01 LT.

The bike came to me with 15,000 miles, and pouring oil from the transmission input seal.

The clutch was slipping. I drilled 2 holes into the bellhousing, one at 6 oclock as a weep hole, one at about 2 oclock, which I used to spray a few cans of brakeclean into the bellhousing and onto the clutch to flush the oil off. It was a long shot, but it worked, the clutch isn't slipping. I also drilled the slave cylinder weep hole, but nothing really going on there.

When the bike came in, it knocked like mad from the transmission, I assume the input bearing. Draining the gearbox recovered 200 ml, less than 1/3 of what should have been in it. I refilled it with mobil 1 gear oil and a couple oz of ATFt o try to soften the input seal. Now here is where it gets interesting. I filled the tranny to the specified level (fill hole) on the center stand, and ran it. The input bearing knocked badly. I then put the bike on the sidestand, and filled the tranny to the fill hole. I was surprised how much more gear oil it took. The transmission really quieted down. Expectedly it drains a few drops from the bellhousing weephole on each ride, but so far the clutch has not slipped.

The work outlined was an attempt to satisfy a friend who doesn't have the money to do a proper repair. It also is what leads to the following question...

Over the years I have generally seen that seals, unless with exceptionall high miles, only give up because of runout in the shaft. The seal can't be expected to follow an eccentric. I also am aware that input bearings on these transmission can be an issue, but I wonder if it might not be that the specified transmission fill level is to low when filled on the centerrstand. Since the tranny is basically splash oiled, I wonder if the volume is marginal to insure oil to the input bearing, and if filling on the side stand might not be a proper long term solution for the input bearing issue?

So the question to those with a more intimate knowledge of the transmission is if, in your opinion, the specified oil level in the transmission might be a contributing factor to the input bearing failures, and if by filling on the sidestand it might not be the way to resolve some of the beairing and attending seal issues?

TIA, Steve
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post #2 of 2 Old May 19th, 2015, 7:52 pm
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Join Date: May 2004
Location: Hazel Green, AL, USA
Posts: 13,306
Re: A transmission question

It is the same as an LT and the bearings are grease filled and sealed. But oil will work its way in there. The input bearing does get a large force on it and I have replaced three so far in LT transmissions. If it is sounding bad with the center stand fill you have a bearing issue. The additional oil is just dampening the sound of the bad bearing.

2009 K1300GT Red Rocket
2009 R1200GS (Gone)
2005 K1200LT Ocean Blue Blue Wizard 110 K and counting...
2006 Bushtec Turbo+2 Spell
2004 330 Ci Convertable

Have ridden a Motorcycle in all 48
But lack DE, MA, RI and CT with the 2005 LT

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