Noisy final drive post-mortem - BMW R1200GS Forum : R1200 GS Forums
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post #1 of 8 (permalink) Old 04-Jun-2018, 05:08 AM (422) Thread Starter
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Noisy final drive post-mortem

Took a few minutes today to dismantle the LC final drive. These are my findings.

BMW have significantly simplified the design. Tapered roller bearings are used on both sides of the shaft to accommodate the axial loads and the casing itself is no longer shimmed. Everything sits in oil bath. Bearing pre-load is set by design and gear clearance might be adjusted by shimming of the bevel gear shaft, I din't dismantle that yet but that seems like the only way of adjusting for correct backlash and teeth meshing. It does not look like there are any spacers used to set the races for correct bearing pre-load.

The wheel side bearing seems too wimpy, the rollers are tiny and judging by common sense to widely spaced, only every other window in the cage is populated. Judging by it's condition and black iron sludge everywhere, this is the bearing that failed and was making noises. The race is scored, wear lines are clearly visible. My guess is that this bearing has a limiting speed that is too low for the application it's put to as smaller rollers have to turn faster for the same angular speed and in effect they work harder.

Bevel gear shaft has two opposed taper roller bearings by the looks of it, they look beefy and should last for ever.

Both gears are in very good condition.

There is no perceivable problem with the bevel gear shaft bearings.

I'll report on all bearing and seal sizes in second part once I get my bearing pullers from the lock-up.
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Last edited by beemerbart; 04-Jun-2018 at 03:32 PM (855).
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post #2 of 8 (permalink) Old 04-Jun-2018, 05:38 AM (443) Thread Starter
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Factual correction: it's the outside bearing that has every other cage slot populated. Wheel side bearing has a fully populated cage, still, rollers are very small.

The bearing pre-load and gear backlash is adjusted by means of spacers under the outside bearing races. The bearings are made in Hungary by FAG.

The seals seem not to be making a good job of keeping the crap out. The space between the oil lip and outside lip was full of oily gunk made of dust and grease/oil, although the was no oil leaks and the gunk did not seem to get in.

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post #3 of 8 (permalink) Old 04-Jun-2018, 06:40 AM (486) Thread Starter
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Looks like I'm going to have to eat my own words, bearings with the needed sizes can't be found at UK retailers and manufacturers numbers don't come up in search, proprietary bearings are suspected at this stage.

Wheel side: FAG 32913 47J 65mm inside x 90 outside x 13.95 outer race width, 17mm total bearing width

Outside: FAG F574737TR1 48J 60mm inside x 85mm outside x 17mm.

Seals and orings are standard sizes and can be bought at retailers for about half the price of BMW oem.

Right seal 75x90x9mm, Left seal 60x75x8mm, oring 138mm x 2.62mm cross section

I'll get exact bearing sizes after I pull the inner races off.

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Last edited by beemerbart; 04-Jun-2018 at 08:21 AM (556).
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post #4 of 8 (permalink) Old 04-Jun-2018, 06:47 AM (491) Thread Starter
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Looks like wheel side bearing shows up, nobody seems to retail it though.

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Last edited by beemerbart; 04-Jun-2018 at 06:58 AM (498).
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post #5 of 8 (permalink) Old 04-Jun-2018, 07:32 AM (522)
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Originally Posted by beemerbart View Post
Took a few minutes today to dismantle the LC final drive. These are my findings.

The wheel side bearing seems too weedy, the rollers are tiny and judging by common sense to widely spaced,..
Had to look up the meaning: “weedy” as I’m from your (former)‘Colonies’ .. <grin>


https://dictionary.cambridge.org/us/.../english/weedy
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post #6 of 8 (permalink) Old 04-Jun-2018, 08:06 AM (546) Thread Starter
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Quote:
Originally Posted by Clay View Post
Had to look up the meaning: “weedy” as I’m from your (former)‘Colonies’ .. <grin>


https://dictionary.cambridge.org/us/.../english/weedy
LOL, got auto corrected on my phone, meant wimpy. Thanks. But weedy means weak, so that actually suitable.

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Last edited by beemerbart; 04-Jun-2018 at 08:10 AM (549).
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post #7 of 8 (permalink) Old 04-Jun-2018, 08:13 AM (550) Thread Starter
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Win! Found the wheel bearing on ebay. NSK made for 90.
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post #8 of 8 (permalink) Old 04-Jun-2018, 08:22 AM (557) Thread Starter
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Code for the left bearing is 4T-32912. 60 x 85 x 17mm.

Found on German ebay and purchased.

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Last edited by beemerbart; 04-Jun-2018 at 03:28 PM (852).
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