Rebild of '79 final drive

[Barry_Ferguson]

Gotta do it.  Oil leaking into brake.  Gotta quote
of $850 (worst case).  Therefore must do it myself.
(I really want to get riding this bike!)

So dove into it.  Removing the cover--piece of cake
so far.  Ten nuts and the threaded holes (5x0.
in the cover are obviously to force the cover off.  Did
that.  From the parts diagram it appears that the next
step is to simply force the crown-gear/spline out of
the cover.  I have a hydraulic press in my shop so I
can surely do that.  I am not worried about the bearing.
I see that it is already toast (rust in the oil--how did water
get it there?).  What
worries me is that I am missing a c-clip or something
and will damage the cover.

What I really need is the procedure.  My Haynes manual
is very disappointing here.  It is completely silent.  (Actually
it says it does not think amateurs will be doing this job    )

Maybe someone can point me to the procedure.  I am sure it
is in the factory shop manual but that has to be very expensive.
If it is somewhere on the net that would be terrific.  Maybe some
kind soul has one of the other manuals and would check for me.

Any help/advice would be appreciated.  Thanks in advance.

Sincerely,
Barry#2
stilllrnn

[Adrian]

http://bmwmotorcycletech.info/manuals.htm

Hi there - this web site has a large number of links to various other BMW bike sites across the ranges and years. Perhaps you can find some info thru this. Good luck .....

[Adrian]

http://www.dansmc.com/shopmanual2.htm

Here's another one that might be useful .... Adrian

[Bob_Roller]

Unless there is corrosion between the bearing and cover, you can use a soft faced hammer, or a piece of wood and a regular hammer to hit the splined output shaft, to remove the bearing /gear assembly form the housing, no other parts are keeping it in there .

There are shims between the bearing and the cover, to adjust the contact of the ring and pinion gears .

[montmil]

Unless there is corrosion between the bearing and cover...

I recently replaced the bearing and oil seal on the '81s final drive. The slined drive to the rear wheel was simply pushed out by hand. I heated the aluminum case and the bearing was also easily removed.

I think Bob may be onto something, especially since you mentioned "rust". A penetrating fluid might help.

And do pay close attention to the shims! You may note that the parts fiche offered m-a-n-y different thicknesses. The drive is set during the manufacturing process using specific tooling... although I'd but old "Gunther" can tell what's right just by the feel of things.

Monte

[Bob_Roller]

I've done all three final drives on my R65's and all of them came apart with no trouble, left the cover out in the sun for about an hour, it was so hot you couldn't touch it with your bare hand (first day of winter here in Phoenix ) I supported the cover on three pieces of wood, the crown gear was about .5 inches off of a piece of plywood, a few taps with a soft faced hammer and they all came apart easily .

[Rob Valdez 79 R65]

I've done all three final drives on my R65's

Did you reuse the shims that were originally in them, or did you have to re-shim any of them?

[Bob_Roller]

Reused the shims that were installed, if you replaced the bearing, you would need to go through the test/adjustment procedure and determine if you had the correct amount of shimming .

[Barry_Ferguson]

To Bob_Roller,

Please, where do I find the procedure to
determine the shimming?

Sincerely,
Barry#2

[montmil]

... where do I find the procedure to determine the shimming?
Barry#2

It would be in the "official" BMW shop service books. Nowhere in any of the commercial manuals available. You'll require some special tools and possible jigs. $$$

Or another potential resource might be Snowbum's site. Surf for other options...

That said, when I replaced the honkin' big bearing in the final drive of the '81, I "miked" both old and new, found them identical and went merrily on my way with the refit. No problemo.

Monte

[Bob_Roller]

The procedure is quite simple .

It requires that you putand I'm quoting the BMW shop manual, engineers blue ink on one of the gears, assemble and torque the cover donw, rotate the final drive 5 or so turns, disassemble the final drive and see where the contact area is on the gears .

You want it as close as you can get to having contact in the middle of the gears .

So you need to find some sort ofink that wont dry too fast and put it on one of the gears, probably the crown or ring gear .  

[Julio A.]

Rust in the final drive could be from the air sucked in via the breather.
I noticed that in the metal plate that surrounds the large crown gear had progressively more rust as you go near the breather.

I replaced my Final drive oil seal thrice within the year. the first two attempts were failures as my rear break would get soaked in gear oil within the first 100 km.

The Third time, I followed Monte's procedure and removed the whole crown gear assembly to properly facilitate the installment of the new oil seal. This time, for extra insurance, I also invested on an original OEM oil seal from BMW. I have traveled at least 700km on this one for around 4 months now and there is not a drop of oil in the rear shoes.

Anyway, the attached picture from the repair manual might help. I only got my cellphone cam at the moment so my advanced apologies for the slightly blurry pic. But i'm sure the words are still legible.

[Bob_Roller]

A picture is worth a thousand words !!!!!!!!!!!

[Barry_Ferguson]

Thanks guys, for the 1000+ words.

Sincerely,
Barry#2