K75-Intermediate housing gear lash, vibration

  • Has anyone ever rebuilt any of the gearing assemblies in the intermediate housing? It looks like the output shaft gear drives other gears, like the alternator drive and starter motor 1-way clutch. The fiche shows several roller bearings, seals, spring washers, etc. that look like they could become a source of low RPM vibrations under different loads.

    Has anyone had any experience with this assembly? Has anyone ever tried to diagnose any rattling from this area?



  • Some things I've found out so far: Bearing failure is not unheard of in the gearing and shafts mounted in the intermediate housing. Here's an interesting link where the bearing behind the alternator driving dog failed: http://k100rt.aforumfree.com/t…ediate-gear-repair-thread

    More interesting info about problems with intermediate housing mis-alignment and distortion. The misalignment issue in some cases could have been due to the sealant between the intermediate housing and the engine block being "wedge shaped" (thicker on one side than the other), causing the housing (and therefore, the transmission) to be misaligned in a way that promotes spline wear. Also mentioned was the housing distortion resulting from an original shipping issue with a block of wood under the transmission (for models palletized and shipped to the US): <!-- m --><a class="postlink" href="http://www.bmwmoa.org/forum/showthread.php?t=51034&page=2" onclick="window.open(this.href);return false;">http://www.bmwmoa.org/forum/showthread. ... 034&page=2</a><!-- m -->

    Anyway, it doesn't seem out of the question that these assemblies could be responsible for low RPM shudder and noise under load. I'm thinking about pulling mine off and having a look around.

    Also, I've been trying to map out what gear drives what. From what I can tell, here's the arrangement:

    1) The gear on the back of the crankshaft drives a gear on the output shaft mounted below.
    2) There's also a gear on the top of the same crankshaft gear that drives the alternator. This gear/shaft/bearing assembly is mounted on the intermediate housing.
    3) Co-located on the shaft that drives the alternator is another gear that drives the 1-way starter clutch. When the engine is running, this gear remains stationary with its shaft and bearings spinning underneath it.
    4) Another 2-gear & shaft assembly connects this 1-way starter clutch gear to the starter motor. When the starter motor is engaged, it turns the large gear wheel, which turns the shaft, which turns the smaller gear, which drives the gear on the 1-way clutch. When driven in this rotational direction, the starter clutch engages by pressing several lobes onto a sleeve connected to the now spinning starter clutch gear. This turns the gear connected to the crankshaft to start the engine.

    So what I can't figure out is this: What does the idle gear on the end of the output shaft drive do? (See #9 on this image: http://realoem.com/bmw/showpar…&btnr=11_1801&hg=11&fg=10). I can't figure out what it connects to. What am I missing?



  • Hello Ty,

    I know 3 constructional revisions made to old K100 - but none for the K75.

  • Quote from "ReneZ"

    Prevent backlash noise.

    Are you saying that idle gear (#9) prevents backlash noise? How does this work? Does this also ride on the same crankshaft gear as the output shaft drive gear it is positioned next to?

  • Look at the drawing; it is fitted 'loose' over the shaft, but is spring loaded, therefore will always keep the actual gears fully engaged once fitted in place. I can appreciate that looking at the shaft in isolation it looks strange, but 'see' it with the other gearwheel, from the crankshaft, in place.

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