Final drive big seal replacement

[Kookaburra]

Feeling really good that at last I have repacked the rear wheel bearings and replaced the seals. Now to replace the large leaking oil seal on the final drive.
I have picked up tips from a search of the site about how to remove the seal-drill four holes, fit self tappers and lever off and when refitting- wrap tape round splines to avoid cutting the seal.

What is not clear to me is whether replacing the seal can be done in situ or whether it is advisable to remove the cardan cover, fit the new seal and then replace cardan cover with a new paper gasket. Advice please taking into account my workshop is a carport and my mechanical skills average.

[Tony Smith]

Remove the cover - IIRC after removing all the nuts you use a pair of 5mm threads to "push" the cover off.

Once off you can remove the seal by whatever meas you fancy. Putting the cover with new seal back on, forget tape, an aluminium beer can with the top cut off and placed over the drive splines works an absolute treat.

Couple of things you ain't going to want to hear.

If the big seal is gonski, then chances are the seal on the input shaft and the hidden seal that a lot of people pretend doesn't exist in the outer housing will probably also be crook or on the way.

[Kookaburra]

Thanks Tony a good tip and an excuse to crack a beer. Don't think I want to go any further in exploration of the seal on the input shaft and the 'non existent seal' in the outer housing.  

Clymers is fairly obtuse about removing the cover talking special tools and application of heat. So now to score some 5mm threads....

[montmil]

Remember to remove the rear brake axle shaft prior to lifting the Cardan cover; which will also require a new gasket. Imperative to clean both the cover and the drive housing gasket surfaces or you'll have another oil leak to deal with. The small o-rings on the brake shaft can be replaced during this relatively simple seal job.

[Tony Smith]

which will also require a new gasket. .

Oh yes, you will never forget that gasket.
If you locked an engineer in a small room and fed them through a hatch and did not allow them out until they designed a gasket almost impossible to clean off (all the studs get in the way, it's narrow and it's fiddly) they would probably have come up with something close to this.

I worked at mine for about an hour and was unhappy with both the progress and the amount of gasket I was not removing - enter 500psi water spray and fine jet.

High pressure spray  ---- 1
Gasket --------------------- 0


Clean, dry and oil immediately after of course.

[mrclubike]

You aint kidding about how hard it is to remove that gasket
That inner seal really isn't that bad to change You just have to heat the housing up and slide the bearing out.
I remember using the rear axle for a installer or remover (cant remember which or if it was both)
A heat gun is one of those handy tools every Airhead owner should have and know how to use

[Luca]

You'll also find out that the big cover gasket only fits one way, so get that figured out before you go to heating the cardan cover for re-install.  After re-installing the heated cover, I tapped mine with a plastic hammer to get the bearing properly seated in the bore because it was a little bound up at first.

After you cut your beer can, make sure to gently sand the cut edges so that they don't knick the seal on the way out.

[montmil]

Note the bottom of the can has rolled edges that aid in easing the oil seal onto the can. Use some light oil on the seal's lip and the can as dry friction might possibly damage the rather fragile seal contact point.

Neatly trim and assure that the cut edge is absolutely smooth prior to lowering the Cardan cover over the can. Otherwise, you may get to do this chore a second time.

Old photo... Rather than blue, the latest Miller Lite cans are white. Lite=Faster  

[Kookaburra]

Thanks for all the good tips and pictures. Now time to fess up about taking some of the advice (but not all of it) and getting into some bother.  So with the cardan cover still in place and the final drive still on the bike I managed to easily remove the existing big seal using the "drill small holes and leverage out on self tapping screws" method.
I then went to the "push new seal over the circumcised beer can method" which got the lubed up seal into position (almost). Unfortunately it became stuck and a little twisted bulging out ever so slightly over the flat of the cardan cover on one side and refused to straighten despite various persuasion attempts. Ever hopeful I refilled the final drive, reassembled the bike and took off to the petrol station to air up the tyres to find (surprise surprise) it was already leaking worse than the one I was replacing!
So here I sit waiting for motobins to get over their Christmas cheer and send me some bits including the big seal so I can try again.

So I ask again, has anyone managed to sucessfully replace the big seal without removing the cardan cover or did I just dream that I saw this somewhere?

[montmil]

So I ask again, has anyone managed to sucessfully replace the big seal without removing the cardan cover or did I just dream that I saw this somewhere?

Dream on, Klingon!

Seriously. Slow down. Keep the Cardan cover level with the final drive case. Use enough lube and go gently.

Hmmm... Last comment sounds rather kinky.

[mrclubike]

I am sure it could be done.
If you can fabricate some kind of seal driver out of a piece of pipe or something you have a greater chance of success.
The hardest part of  doing it the other way is removing the gasket.
Another reason to remove the cover is you can see were the wear grove is and try to install the seal in a position were  it will ride in a different place  

[montmil]

I am sure it could be done. 

Not really. If you'll check the photo I posted of the Cardan cover, you'll note the circular, raised ridge behind the cast 'spokes'. The interior area of that 'ridge' is a machined location that accepts the seal. No way to remove nor replace the seal without removing the Cardan cover. Both Haynes and Clymer manuals confirm this.

You do make a good point regarding positioning the seal's lip in an unworn area of the spline hub. I did that on both my '81 R65 and the '78 R100S. Anything to stop oiling your shoes!

[Bob_Roller]

I suggest removing the cover and replace the seal that way .
A bit of work the first time, with the factory sealant / adhesive .
A can of gasket remover will make the job less tedious .
I use an oil filter tool for an oilhead, to drive out the seal and reinstall it, works great .
I also have used heavy clear adhesive tape over the crown wheel splines, have not damaged a seal yet and I've done this four times .
I heat the seal as well before installation, couldn't tell you the temperature, as I just put it out in the sun along with the cover, usually need gloves to work with them on assembly .
One thing that hasn't been mentioned, is replacement of the rear brake camshaft seals, if your bike has them, can't tell what year bike you have .

[Kookaburra]

Things just get ever more curious. I have now managed to leverage off the cardan cover using the two 5mm screw method however the whole box and dice came off with it including the rear gear assembly and an internal metal baffle (designed it seems to distribute oil in particular directions)  This baffle doesn't appear in any of the Clymer diagrams/photos or the BMW diagrams for this model. Not really an issue however...
I have cleaned up both gasket surfaces and removed the big seal but the cardan cover, ring gear and bearings are all still determinedly united on the work bench.

So what do I do next?  It is not clear how the cardan cover separates from the ring gear and how to put all this stuff back into the final drive well correctly.

[mrclubike]

One of the special tools all air head owners should have is a heat gun.
Don't try to beat aluminum cases to disassemble.
You will need to simply support the assembly with a couple blocks of wood under the cover
Then heat the cover until  the ring gear with bearing  falls  right out.
You can use a torch but is not really recommended.
The back bearing needs to be removed if you replace that seal also.
Same kind of deal  
Just heat the housing until it slides out
replace the seal
reheat the housing and slide the bearing back in.