Rear Drive Input Nut

[Air4Life]

I've been doing some snowbum reading on rear drives and the following jumped out at me. � I then went to the Max Parts Fiche with hopes of having the illustration make it more clear to me. � 

Unfortunately the terminology is not the same when describing the "rear drive input nut" or I'm just looking in the wrong place. � If it is the right place, then my guess it would be � No. 01 part "Collared Nut" or possibly No. 06 "threaded ring". � But I'm not sure...

My other question is, is this something that would give warnings - in other words, noises? � I would think if there were audible noises while riding it would be to late for those parts... � Anybody find theirs loose? � Is there some way to check without disconnecting the rear drive from the shaft and the rest...? � Looks terribly expensive to have the crown gear set wiped out, just because it was loose. � 

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http://bmwmotorcycletech.info/rearwhlsplines.htm

If oil is moving from the driveshaft housing and going into the rear drive, there are a few possible causes:

1.  The rear drive input nut is loose.  That MUST be corrected immediately!...it can cause major damage to the rear drive.  Whether or not oil is migrating, if you ever have the rear drive off the driveshaft housing, DO check that input nut!!!   This applies to ALL MODELS OF AIRHEADS.

Max Parts:

01 23 21 1 230 084       COLLAR NUT

06 33 12 1 230 355       THREADED RING


http://www.maxbmwmotorcycles.com/fiche/DiagramsMain.aspx?vid=51897&rnd=08102012

[Barry]

If oil is moving from the driveshaft housing and going into the rear drive, there are a few possible causes:
 

Snowbum absolutely knows his stuff but I don't recall a loose driveshaft nut ever being reported here.   If you do have oil migration I wouldn't necessarily conclude that it was due to this nut being loose.

When oil migrates to the rear drive I would say the most common cause is an excess volume of oil in drive shaft. It's generally accepted that 100cc is the maximum volume of oil to use in the drive shaft and some say even less is OK.

Ignore the Riders Manual method of measuring a level of 2mm with a dipstick through the filler hole. The internal drive shaft is in the way so if you can see an oil level to measure with a dipstick there is definitely too much in. I believe this is an erroneous description which got messed up in the translation from German.  There is sufficient oil if the drive shaft picks up an observable film of oil when the rear wheel is rotated by hand. I.E if the oil level is high enough to touch the underside of the drive shaft that's enough.

[tvrla]

I've never checked the torque on the input side nut. Don't know of or heard of anyone doing it. And, to compound that - I sort of dimly recall one being loose once. But I may be wrong about that.

The other cause of oil flinging out the final drive breather is a worn out transmission output seal. That was my first airhead lesson back in 1990 - just got the bike and oil was flinging onto the tire...

Not a pleasant discovery!

A transmission output seal fixed it! But it took me several months to collect the tools and parts to get the job done. I was kind of destitute back then.  

[Burt]

I hope I am not hijacking this thread with my question.

Further to this I had the Bevel Drive off over the weekend because I have had a slight weep around the rear axle (wheel spindle) nut.  I did toy with the idea off dismantling the bevel drive but decided against it.  As the bike has been sitting for quite a while I believe it may be a static leak only.  

Whilst on the bench there was a fair bit of crud just in beneath the nut you are talking about.  i.e. lowest part of the system.  

As the Haynes manual states (8.3.2) “a faulty output oil seal will be indicated by excessive oil in the brake drum, or around the wheel spindle nut”.  My interpretation of this is the seal, item 5 in the above diagram.  

As the brake pad area inside the hub of the wheel is bone dry and my “slight weep” is more of small muddy pool of oil I am reluctant to disassemble the entire bevel drive for a static weep.  My guess is that when I put the bike back on the road and start riding it, the weep will probably stop.  If it then turns into a dynamic leak then I know I have a problem.  

Incidentally when I checked the transmission/drive shaft and the bevel drive oil levels, the drive shaft appeared to be low and the bevel drive appeared to be overfilled.  

Does anybody recommend pulling down the bevel drive?  To me it is just a 90 degree gearbox.  

The bike has 92K, Kms on it and the drive shaft/bevel drive splines have minimal wear.  

Thanks Barry, I guess I shall have to use a syringe for an accurate level in the drive shaft from now on.  

Cheers, Burt.  

[Barry]

My guess is that when I put the bike back on the road and start riding it, the weep will probably stop.

I think that's a good approach. When I first got mine it had done only 6000 miles in 28 years so must have had long periods of inactivity. I also had oil migration into the bevel drive at the first oil change but it never happened again once the bike was put back in regular use. A weep from the rear main seal also cured itself.

Does anybody recommend pulling down the bevel drive?To me it is just a 90 degree gearbox.

I agree. The bevel drive is relatively low stressed in fact very much so compared to a typical off set hypoid car differential. As long as the initial shimming is good they seem to last pretty much for ever.  

[Bob_Roller]

If you do replace the output seal on the final drive, the paper gasket that goes between the cover and housing, only goes on one way .

So, make sure if you use any kind of sealant on the gasket, you have the gasket marked and get it on right the first time .

I've replaced the output seals on all three of my R65's, it's a straight forward job .

Heat the cover before reassembling it, the fit between the cover and the bearing on the crown or ring gear is quite close .

[Burt]

Thanks Barry & Bob.  

You have pretty well confirmed what I thought.  

As for heating the cover on reassembly, I might just sit it out in the sun for a couple of hours on the concrete.  Should do the job.  

Cheers, Burt.  

[Air4Life]

Ignore the Riders Manual method of measuring a level of 2mm with a dipstick through the filler hole. The internal drive shaft is in the way so if you can see an oil level to measure with a dipstick there is definitely too much in. I believe this is an erroneous description which got messed up in the translation from German.  There is sufficient oil if the drive shaft picks up an observable film of oil when the rear wheel is rotated by hand. I.E if the oil level is high enough to touch the underside of the drive shaft that's enough.

At first I had filled it to the 150 cc mark.  Then after the initial trouble, that which prompted this thread, I was thinking that it was a result of the cold weather.  I then followed up with  the suspect owners manual method above.  Well, after I had ridden it for a while and worked the brake dry a few weeks back, the brake has begun slipping some.  Yes its cold, but I'm not certain that's the cause.  I'm afraid its likely a compromised seal.  

For the sake of desperation, let's not remove the possibility that we can follow the method you described above.  Does having just "enough to touch the underside of the drive shaft" suggest that it will stop leaking?  I'm reluctant to let this be as I don't know what to expect from operating at such a perceived low level.  

[tvrla]

G/S driveshafts run dry and they last anywhere from 30K to 100K before the ujoints go. All you really need is an oil film - it's not like they need to run in an oil bath. The spinning driveline will sweep the oil into the air making one big oily mess of everything. So don't worry about it.

[Barry]

Does having just "enough to touch the underside of the drive shaft" suggest that it will stop leaking?  

I suppose not if the seal is gone but running the correct level does at least give the seal a fighting chance.  

As Wirespokes explained, there is no need to be concerned about the lower volume of oil. This a universal view in the airhead community with some guru's saying anywhere between 50 and 100cc is enough.

If you really want to be sure there is enough oil in, drain it out and put it back again. Because you don't get every last drop out if you have anywhere near 100cc there was enough. More than 100cc and there was too much.

I know it would be nice if there was a simple definitive level measurement but as mentioned earlier I'm quite convinced that the method described in the manual is wrong.

[Air4Life]

Very good.    

As a matter of fact I did drain the original quantity and found it to be around 85 cc - that is,  65 cc less than what was originally put in.

Much appreciative.