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Thread: New member, new owner, new rider - new problem

  1. #1

    Getting back to the topic at hand...

    Further draining/disassembly was carried out tonight, and here are my findings:

    * The final drive was filled with fluid. Not anymore, because it's now draining into my catch pan.
    * Same situation with the driveshaft housing. This fluid was lighter in color than the final drive fluid. I believe this to be because either A) it's a different fluid, B) it's not as old as the other fluid, suggesting inconsistent service intervals in this bike's past OR
    * C) the amount of fuzz on the final drive drain plug suggests the fluid in the final drive simply has more contaminants. I was surprised at the mound on the plug (similar in quantity to the transmission), but this being the first time I've drained this unit on any bike at all, it could be perfectly normal. It was all fuzz, no grit.

    Next, I figured I'd continue on to the next step in tear-down and remove the final drive. Here I found something awry - the big nut holding the final drive unit coupler was literally less than hand tight. Loose, flailing in the wind, about one and a half threads away from completely unattached.

    Spinning the driveshaft by hand after the final drive was removed, I felt no slop in the u-joint. Doesn't mean the joint is good until I pull the shaft and really inspect for play, but on cursory glance, it's looking fine.

    Back to the loose nut - what torque value does this guy need to be tightened to? Additionally, any ideas as to what symptoms this would present? Does this nut occasionally back out, or is this indicative that monkeys have been here before, and I should inspect further?

    Thanks again, guys!
    1983 R80RT - 48kmi+
    plus too many old Mercedes to mention!

  2. #2
    Liaison 20774's Avatar
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    My thoughts...

    The fuzz you talk about is probably normal. As long as there are no flakes or large pieces of metal. But, fuzz is pretty normal.

    Lighter colored oil in the driveshaft could possibly be normal as it doesn't see as much work/thrashing as the tranny and final drive do. Or it could be some water got mixed in with it. Water will turn the oil a creamy coffee color.

    The big nut should be very tight. The large bevel drive pinion nut on the final drive for an '83 R80RT should be around 120 ft-lbs...I think that's the nut you're talking about. It usually takes special tools and ways to counter that kind of tightness. I'm wondering if this wasn't the whole problem all along... I can't see this coming off on it's own, but I believe I've heard about it from time to time...
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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