Leaky final drive.

[goanna_38]

Hi all,

        I’ve developed a leaky final drive seal (the big one on the wheel side) and a replacement should be in my hot little hand in a day or two. I’m just after advice on installing it. Oil on the inside of the seal is obvious, but what do I put on the outside? I’ve had 3 different loads of advice thrust at me so far.

1/ Dry. Not a fan to be honest.

2/ A non-hardening gasket cement like Permatex no.3

3/ Same oil as the inside face of the seal.

I’ve got to admit the oil sounds like it’d work, because there’s not really any sort of pressure in there and the whole point of the exercise is to get the seal seated with a minimum of fuss and bother, but I thought “Hmmm BMW might have their own way of doing things.” (3 switch indicators anybody?) so it might be worth running it past the collective. I tried a search but found nothing. It’s probably there, but I can be an unimaginative searcher and draw blanks in relatively target rich environments. Many thanks  in advance for any advice offered.

[King Herald]

I changed my seal a month or two ago. Pulled the old seal out using a self tapping screw and some leverage, cleaned everything up, made sure the sealing surfaces were clean of any deposits or buildup, then tapped the new seal in, dry. It went in quite easily. 
I used the old seal to help tap the new in, keeping it square and even until it was at the right depth. 
 

I had several people tell me I should have changed the bearing too, as that’s one reason the seal leaks, but I didn’t find any metal when I strained the oil through a paint filter, nor did I feel any play or roughness in the bearing. 
 

Youtube has several videos showing how it is done. 

[Jim Moore]

The bike usually leaks from that area because the bearing behind it has gone bad and destroyed the seal. Take a good look at the bearing. It will be very obvious if it's bad. King Herald's and mine were OK, but most are def not OK. Good luck.

 

I think I pressed that seal in with my thumbs. It went in very easily.

[dirtrider]

Morning  goanna_38

 

From the BMW service manual___  " Lightly oil the lip and outer edge of the sealing ring". (bold is my highlighting)

 

As Jim & King Herald mentioned, be sure to check the crown bearing. Bolt the wheel back on then give it a good top/bottom & front/rear wiggle to see if there is any bearing play. 

 

Then once the seal is removed clean the bearing (that you can get to)  then look for pitting in the races & nice even ball separation with the ball separators looking OK.  A big failure point in the crown bearing  is the ball separator failing. 

 

Try your darndest the get the old seal out without bending, denting or major damage as the old seal makes a great new seal driver (just flip it over). It looks like you are pressurizing the final drive with air pressure, don't overdo that but leaving some air pressure in the drive might help the old seal dislodge easier.  

 

I see some oil coming from farther forward so loosen the swing arm boot rear zip tie then see how much gear oil is in the boot from a leaking pinion seal. 

 

If you are/were using real synthetic gear oil then think about switching back to conventional gear oil as that can slow stop a pinion seal seeping.  (pinion seal replacement is a real pain)

 

If something doesn't seem right with the bearing you can easily remove the side cover (it will come off with the spool & ring gear included with it). Not a big deal but you should install a new cover "O" ring if you remove it. (caution: if you do this & then pull the spool & bearing out of the side cover keep track of the bearing preload shims so as to not loose any as those need to go back in). A little heat on the cover in the bearing area then the spool & bearing will pull right out of the cover.

 

 

[King Herald]

Good point DR mentions, lubricating the actual seal lip and sealing surface when installing the new seal. I forgot to mention that. 
 

This was how I got my seal out, drilled a small hole and screwed a self tapper in. Keep the screw upright, so not to damage the sealing surface as you lever on it. 

 

 

 

[goanna_38]

Ok, the consensus seems to be to check the bearing. I haven't pulled the seal out yet because I haven't got the replacement seal but I did bolt the wheel back on and give it a good back and forth to see what I could feel. If I rotate the wheel as per normal it feels about how I imagine a helical final drive set would feel once all the oil has drained (I drained the oil a couple of days ago), nothing graunchy that I can feel, just the gears interacting. If I grab the wheel and wriggle it back and forth to check for play there is just the faintest feeling of play, but I can't actually see anything moving. I assume it should have a tiny amount of play in it. I could only feel play when shaking it top and bottom, if I grabbed the font and back I couldn't feel any play, but then again I could barely feel play in it at it's worse. I initially screwed in 2 bolts and shook the centre about and couldn't feel anything at all, it wasn't until I mounted the wheel that I could feel anything at all. Again, it's empty of oil so I imagine most of the play will be because it's not sitting in an oil bath. 

Or am I deluding myself and it's buggered? I'll see what I can see when I pop the seal out. From what's written above I assume if the big bearing does need replacement it's just a straight swap, taking care to fit the original shims and no further arsing about with shims required?

[dirtrider]

2 hours ago, goanna_38 said:

Ok, the consensus seems to be to check the bearing. I haven't pulled the seal out yet because I haven't got the replacement seal but I did bolt the wheel back on and give it a good back and forth to see what I could feel. If I rotate the wheel as per normal it feels about how I imagine a helical final drive set would feel once all the oil has drained (I drained the oil a couple of days ago), nothing graunchy that I can feel, just the gears interacting. If I grab the wheel and wriggle it back and forth to check for play there is just the faintest feeling of play, but I can't actually see anything moving. I assume it should have a tiny amount of play in it. I could only feel play when shaking it top and bottom, if I grabbed the font and back I couldn't feel any play, but then again I could barely feel play in it at it's worse. I initially screwed in 2 bolts and shook the centre about and couldn't feel anything at all, it wasn't until I mounted the wheel that I could feel anything at all. Again, it's empty of oil so I imagine most of the play will be because it's not sitting in an oil bath. 

Or am I deluding myself and it's buggered? I'll see what I can see when I pop the seal out. From what's written above I assume if the big bearing does need replacement it's just a straight swap, taking care to fit the original shims and no further arsing about with shims required?

Morning goanna_38

 

Typically, when you get some movement when wiggling top & bottom but no movement when wiggling front to rear you have movement in the swing arm to final drive bearings. 

 

If you have movement then you need to check for actual movement between the wheel & the final drive housing (I usually use a dial indicator for measuring this).

 

That crown bearing is originally set up for a specific  preload (no bearing movement) but on older well run-in motorcycles they can develop a little movement but there is a fine line between a little bearing play & bearing starting to fail. 

 

So, you probably should follow up & determine IF the movement is between ring gear spool (basically the wheel) & the final drive housing, or if it is just swing arm to final drive pivot bearing play. 

 

If you get someone else to wiggle the rear wheel you can wedge your finger in between the brake rotor & the solid mounted caliper mounting bracket. If you have movement between those then you have some bearing wear. If the rear wheel moves but no movement between the brake rotor & the caliper solid mounted bracket then your movement is most likely in the swing arm to final drive pivot bearings. 

[dirtrider]

3 hours ago, goanna_38 said:

 From what's written above I assume if the big bearing does need replacement it's just a straight swap, taking care to fit the original shims and no further arsing about with shims required?

More,

 

I will address this in a separate reply.

 

Some try it this way (JUST swap in a new bearing using the old shims), sometimes it works & sometimes it doesn't work. 

 

If you don't trash the new bearing in about 5000 miles then it worked OK. 

 

Problem is, you really don't know how close the new bearing is to the old bearing. BMW has changed those bearings a couple of times since your motorcycle was built. There was 17 ball & a 19 ball bearing at one time or another. 

 

I have "just" swapped in a new bearing when I had to (like replacing a failed bearing on the road part way through a trip) not my motorcycles but the (just swapped in) new bearing allowed completion of a long trip. 

 

In my shop I NEVER just install a new bearing without properly setting the bearing preload, sometimes it ends up with the same shims & other times they require less or more shimming to obtain proper bearing preload. The one thing I hate more than installing a new bearing is to have to buy another bearing THEN setting it up properly. Especially if it fails on the road far from home. 

 

There is a tapered bearing on the other end of the spool so if that wears (or is worn) that also effects the crown bearing preload. 

 

The PROPER way to set that bearing preload is to use the BMW required setting fixturing but almost no one has those at home.

 

There are some (many) work-arounds, some work pretty good, others are more of a hope-it-works than it does work to get proper preload. 

 

It kind of boils down to what a person has available, how adept they are at making what they have work, how creative they are, & how precise they want to be. 

 

Even taking the removed drive to a BMW dealer or repair shop doesn't guarantee it will be done correctly as a lot of shops no longer work on the older BMW motorcycle so unless you get a tec with a background going back that far, or a younger one that has good work ethics, then they might just toss a new bearing in using the old shims as they know it probably won't fail until it is far from their shop in the future.  I would imagine that a lot of shops no longer have ALL the parts still in the shop for proper 1100/1150 bearing preload set up.