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Discussion Starter #1
just got back from dealer in charlotte, I asked him if there were any tell tale signs if the rear drive about to fail, he stated" ride the bike for 60 or so miles, get off put the back of your hand on the rear drive, if it is hot enough to burn your hand then you have a problem. If only warm then dont worry about it.
 

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Don,t forget to take some eggs and some bread with you, as you might be able to fry your own breakfast on your rear drive if it,s on it,s way out.

04 your 05
graphite in Blighty
 

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Not sure I agree completely with his conclusion. I just had my rear drive bearing changed and although the temp has gone down slightly, the old bearing at 56k looked in perfect condition and will be saved as a back-up or emergency replacement. Even the seal could be re-used in a pinch. IMO it is a quality issue. The drive housing is still very warm to the touch after riding, but I think some of this heat is due to the floating brake roter.

The load and the harder and more curves you ride, the warmer the housing will become. The 1st 56k were ridden 99% two up and heavy with some great curves, and now even with the new bearing the housing is very warm to the touch. I wish I had one of those laser heat sensors to compare the temps before and after, but I don't think it has gone down that much with the new bearing. I checked it frequently on our recent trip to Phoenix and back, and always found it rather warm to the touch. Previously there had been times during hot weather, which is another factor, the housing was so hot you could not hold your fingers on it without being burnt. But on our trip of 2880 miles, you could touch it without being burnt, but would not want to hold your fingers on it for very long. The ambient temperatures ran from 38 to 95 degrees during our trip. So although heat may be a factor, I don't think it is a warning for failure, but that's just my opinion.

According to my dealer, who experienced the dreaded rear end failure on his 91 LT in the middle of Texas Big Bend country, he thinks the older bearing was used on older lighter BMW bikes, and was just carried over to the LT without concern for weight and stress, whereas the new bearing has been load tested to better withstand the load and stress found on the LT. Only time will tell if he is correct. Prior to his failure, he felt there probably wasn't a problem, but now sings a different tune and advised me to change the bearing, but admitted the old bearing looked to be in excellent condition.

So, it's kind of like a poker hand, you have to play with the cards you were dealt. Some of the older bearings may run a long time, and 4-5% will fold early. Time will tell if the new bearing will yield different results. :crazy:
 

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Rear drive

The wife and I went for a ride this afternoon. A nice day with the temp in the upper 70s. When we got home, I put my hand on the rear drive and to start with it was nice and warm, but as I held my hand on it it became uncomfortable, and I had to take my hand away after 10 seconds. So what is a successful test-to be able to touch it or hold your hand on it for a period of time?



Bob Schrader
Wentzville, Mo.
'00LTC
 

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Discussion Starter #5
Going by what the tech at the dealership stated, and I took it at face value, If you put the back of your hand on the rear drive after a 60 or so mile ride and it burns your hand, (this is right after you stop and immediately check the rear drive) then you have a problem. Whether this is true or not I do not know, just sharing some info from the tech at the dealer, maybe he had this happen to him on his bike and his rear drive failed.
 

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sheldan2 said:
Going by what the tech at the dealership stated, and I took it at face value, If you put the back of your hand on the rear drive after a 60 or so mile ride and it burns your hand, (this is right after you stop and immediately check the rear drive) then you have a problem. Whether this is true or not I do not know, just sharing some info from the tech at the dealer, maybe he had this happen to him on his bike and his rear drive failed.
ALRIGHTY, THEN!! Let's nip this one in the bud:

There is **NO** correlation between final drive temperature and bearing failure in this application. The amount of heat generated in the final drive is primarily a function of the amount of power fed through the drive -- the heat is due to the parasitic energy loss as the power is transferred through the gears (the final drive, like the tranny is not 100% efficient). The couple of percent of power lost in the power transfer has to go somwhere -- here it is converted to heat.

Proof of this was posted in the last year or so: two LTs travelling together, one one-up, the other two-up and heavily loaded. An infrared thermometer showed the two-up drive ran a fair amount hotter -- consistent with the additional power required to propel the bike down the road. No surprise there.

Also, the fact that you can't hold your hand on the drive long is normal -- the light, relatively low power airheads in my garage also get hot enough to be too hot to hold, and these drives are certainly don't fail with any frequency.

As a last thought, remember that the bearing is in an oil bath. Oil is both a lubricant, and a *highly* effective heat transfer medium. If any significant amount of heat was being generated by the bearing, it would be quickly carried to the housing walls to be dissipated. Moreover, the amount of heat the bearing generates must be a fraction of what the power loss is -- otherwise, if the bearing were generating enough heat to be the source of a "hot" final drive (heat which would be being generated by friction), the friction would have to be so high that it would *immediately* destroy the bearing.
 

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I'm thinking "preemptive replacement"

Gary,

Would you mind detailing exactly which rear drive parts you had replaced and the associated costs? Mine is a 99 also and will be going in to Bob's BMW in several weeks to replace the rear engine seal. At least, we think that's the cause of the oil leak. So, I'm thinking of a preemptive bearing swop while they have it all apart anyway.

Did you replace yours with the newer 17 ball bearing version? I wasn't sure that this was even available for a 99.

Thanks in advance for the info.

Joel Adler
 

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i used the same litmus test the first time i took my bike to a dealer for service. when i saw the amount of the charge i rested my hand on my rump and sure enough, it was VERY hot! proof positive that i'd been abused and was on the verge of breakdown.

;-)
 

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Joel,
The new 17 ball bearing fits all models. If piece of mind is more important than the 180 bucks for the bearing, by all means change it. I am going on some cross country trips this summer and I will feel better with the new bearing. I bought mine last week and will change it one weekend real soon.
 

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Fwiw

I used to carry one of those infared temp readers and at every stop would check the rear drive. Seemed to like running between 125 deg. F to 140 deg. F. depending on the circumstances. One up, two up, loaded, pulling a trailer, 80w/90wt dino, Mobil 1, BMW Synthectic 85w/140 in any combination and never did see it any different. 140 deg. won't burn you, but it does get your attention!

:D :D
 

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You can also get tire temp and pressure reading from the SmarTire system. Works great.
 

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Dman said:
I used to carry one of those infared temp readers and at every stop would check the rear drive. Seemed to like running between 125 deg. F to 140 deg. F. depending on the circumstances. One up, two up, loaded, pulling a trailer, 80w/90wt dino, Mobil 1, BMW Synthectic 85w/140 in any combination and never did see it any different. 140 deg. won't burn you, but it does get your attention!

:D :D
Sorry for resurecting an old thread but.

I'm fairly new here but rode with many experienced people but wasn't our temps. in the 165 range John when when you tested them? I would say thats a big diference from 140. I was even running Redline.
 
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