[murray]

I know this should be posted in the main final drive thread.... but. This post from the LD board describes how to exchange the crown bearing and seal without removing the FD. Assuming the diagnosis made early.What do you think ?
Pete

From: "Dick Fish" <[email protected]>

Subject: [LDRider] BMW Rear Drive Bearing
To: <[email protected]>
Cc: [email protected]
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<refish%[email protected]>

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List
After some thought I will try to explain my experience with this BMW
weakness. I apologize in advance to all the non BMW riders on the list but
have been asked to add some details so will try to do the best I can for
those who care. For the people who know it all with Clymer manuals and the
"I've read or heard" knowledge or my mechanic "said" hit the delete key now.
I believe it is common knowledge that this bearing is a weak point in the
BMW rear drive. I presently own five BMW's of which four use the identical
bearing and seal. As I said earlier I have replaced three. As said very well
by David E.B. Smith the biggest problem is that most dealer's don't stock
the parts.If you carry them you eliminate this part of the problem. I also
agree with David's comment "If you have the bearing and
seals and can replace them before the whole drive gets trashed from lack
of oil and are mechanically skilled, you could handle probably 95% of
final drive failures."
This leads to catching the problem before it becomes more than the bearing
and seal. My experience indicates that a grinding noise will be audible
before you destroy the crown and pinion. Better than that is finding the
very small flakes of the inner race of the bearing before any noise starts.
You will find these on the drain plug magnet.These are extremely fine at the
beginning but the magnet shows that they are steel. If you remove and
examine the inner race of the bearing with a magnifying glass you will see
the initial breakdown. My answer to this is to change the rear drive
lubricant at every engine oil change which gives me the chance to inspect
the magnet. Very cheap insurance I believe.
Now to the interesting part that I'm supposedly not able to do.I believe
almost anybody can do this if they set there mind to it. I have a long
mechanical background so might have some advantage on some but this is not
rocket science.To clarify when I say on the road I would hope to be at a
service station at the least. You will need heat to accomplish this which
you must carry, buy, or borrow. A heat gun is the best but a propane torch
will work.
Remove the rear wheel and brake disk as required.
Using a 7mm Allen wrench ( which is not in the BMW tool kit and does
not come in most sets of metric Allen wrenches. I ordered mine separately
and carry one in each toolkit ,A long handle or socket driven works best.)
Remove the aluminium housing which carries the seal, bearing, crown gear and
shaft.
Gently heat the aluminium housing around the seal. The crown gear, shaft,
and bearing will fall out of the housing with no help when the housing is
warm enough.Be careful not to let the crown gear fall and hit something.
There will be a shim or possibly two that is between the bearing and the
housing.This is what sets the gear lash in part and lets you replace the
bearing without redoing the gear lash if you accept the fact that the
tolerance on the bearing width is for these purposes identical.This part is
very easy because you are dropping steel out of aluminium.
The next is a little tougher because you are removing steel from steel.You
must heat the bearing while keeping the shaft cool. A wet rag on the shaft
after heating the bearing usually works. This is where I use the screw
driver unless I have a set of pullers to remove the bearing from the shaft.
The reassembly is much easier because you can heat the inner race of the
bearing while keeping the shaft cool. If at home I put the shaft in the
freezer and the bearing almost falls on. Make sure the bearing is fully
seated on the crown shaft At this stage remove the seal from the housing
and make sure the shim is replaced with the groove being perfectly clean.
Polish the end of the shaft where it is going to turn in the seal. Reheat
the housing and drop the shaft and bearing assembly into the housing making
sure it is fully seated against the shim. Replace the seal from the outside
being careful not to push it past flush with the housing. There is a small
o-ring around the outer edge of the housing that probably should be replaced
for good shop practice since it is a low cost item. Reassemble and you
should be good to go. If you are not comfortable with your torque skills
have the bolts re-torqued when a torque wrench is available. I hope this
does not sound complicated. I don't feel it is but others may have less
experience. At the very least I would carry the parts so a mechanic could do
this. If you feel comfortable with it I suggest you replace as described at
home and then carry the removed bearing and a new seal as your spares. Then
you will be confident on the road.
I hope this helps.
regards ref

 

[CharlieVT]

Re: Final Drive on the road repair

Great post, thanks.
As someone who has been carrying a crownwheel bearing and seal around in my sidecase for some time I was very interested to read someone's description of a bearing change using the existing shims. Without the special tool to make pre-load shim measurements the process sounds pretty straight forward. I was also interested to read that the bearing can be removed and installed with heat/cold alone without the use of a bearing puller or a bearing press.

 

[PeteM]

Right on, just mike the old bearing it has to be close.
Pete aka murray

 

[tliu]

Thanks for the excellent post!

 

[murray]

Moderators should this not be put in the hall of wisdom ?
Pete

 

[MajNullo]

Bearing Change!

I used the procedure given here to change my bearing. It was going bad at 22,000 miles.
The bearing was pulled from the shaft at a shop. The replacement was done with heat and cold as described. It was just several hours work on one weekend.

 

[JPSpen]

Pictures please

Maybe someone could post the pics of the steps...This would help those who don't intimately know the parts to be better prepared.

Good post.

John

 

[gsgeorge]

Can you post the pic for us to visualize it.

Thanks
:wave

 

[rattler50]

That was a very helpful post. I never thought of that. It should have entered my mind because I was thinking of installing my FD and then checking the lash described in the Clymers manual since I didn't have the tool to lock the driveshaft in place. I was just thinking yesterday that I carry all the tools to fix the FD except the 30mm adapted socket. This way you don't need it. All I have to do now is carry a bearing and a seal and I can put the FD failure out of my mind. I used to heat aluminum tail housings on front wheel drive transmissions to get the bearing race out. A little heat and it would fall out on your feet. I'm with you on the bearing failing over time. I think you will see signs of it in most cases if you keep a close eye on it. And make sure you remove all the debri when you replace the bearing. Some might be hiding around the input shaft. A little carb cleaner should do the job and some compressed air................

 

[rattler50]

PS..............and I found the crown bearing locally and could have gotten it the next day for $160 from a local bearing supply house....the seal probably only comes from BMW. The bearing was in Houston but my seal was still good. It wasn't leaking.......

 

[garry_kramer]

PS..............and I found the crown bearing locally and could have gotten it the next day for $160 from a local bearing supply house....the seal probably only comes from BMW. The bearing was in Houston but my seal was still good. It wasn't leaking.......

What was the part number of the bearing?

 

[fpmlt]

Very helpful, and timely post, as I had just PM'd CharlieVT about pulling the FD just to check that shimming was correct. This rebuild assumes that the shims are correct: does that present any special problems in anyone's view?

 

[CharlieVT]

Very helpful, and timely post, as I had just PM'd CharlieVT about pulling the FD just to check that shimming was correct. This rebuild assumes that the shims are correct: does that present any special problems in anyone's view?

No one knows for sure the cause of crown wheel bearing failure, but improper preload is high on the list of suspects. (Number 1 suspect in my opinion, and I am not alone in this opinion).

Changing a bearing and seal without removing the final drive from the bike would be a quick way to get back on the road but you are not going to easily check for proper preload without removing the drive from the bike.


If you are rebuilding a drive in the hopes of having a long lasting trouble free drive, measure the preload and do it carefully.

If you have a breakdown on the road and just want to get going again, and you have a bearing on hand, just removing the FD cover to install a new bearing using existing shims without removing the whole final drive makes sense, but I wouldn't trust that rebuild over the long haul. The odds of the bearing preload being wrong are too great.

Want to be really cautious? Remove your final drive from the bike. Remove the cover and shims. Measure the existing bearing for preload, and compare your calculations to the shims that were in there. If the shimming is correct, save the shim, if not get the correct shim(s) for that bearing. Remove the existing bearing as gently as possible by heating the bearing and cooling the crown wheel before pulling the bearing. Save the original bearing and its associated shim(s) as a spare in your side case. Install a new bearing and measure for proper preload for the new bearing.

Now you have a rebuilt final drive that has been carefully checked for preload, and you have a spare bearing with a proper shim in your side case for an emergency. I have been riding with that arrangement for over 40K and I don't worry about my final drive failing at all.

 

[Voyager]

Very helpful, and timely post, as I had just PM'd CharlieVT about pulling the FD just to check that shimming was correct. This rebuild assumes that the shims are correct: does that present any special problems in anyone's view?

I don't believe that changing parts in ANY bevel/hypoid final drive without checking the setup is an advisable procedure. As an emergency roadside repair, sure. As a "do it right" permanent repair, no way.

 

[rattler50]

The numbers I gave came from my bearing race. The lady said they were good numbers. They are 61917C3. And yes, this is a roadside fix that can be accomplished with tools I carry and the use of a small press or a large rock and a stick.........

 

[CharlieVT]

The numbers I gave came from my bearing race. The lady said they were good numbers. They are 61917C3. And yes, this is a roadside fix that can be accomplished with tools I carry and the use of a small press or a large rock and a stick.........

A little more seriously, this "roadside repair" could be done with the help of any local mechanic with bearing pullers and a press, or a place with an oven and a freezer, or a propane torch or heat gun and a bucket of ice, and a couple of big screw drivers or other tools to pull the old bearing off the crown wheel.

The only real challenge is going to be removing the old bearing from the crown wheel and installing the new one without stressing the balls and races. Someone did report wrestling the old bearing off the crownwheel without shop tools, but it was reportedly a struggle.

A large rock and a stick? Take photos of that for us!

 

[ez_rdr55]

I carry a #9 rock and a sharp stick just in case.

 

[rattler50]

My puller was a little too thick to get in the slot under the bearing but when I tightened it, the bearing came up and as I tightened it some more, the bearing popped off quite easily. I pressed the bearing back of after a little heat and it almost fell on. I heated the housing and it fell in. Without a heat gun it would be impossible. All in all it was fairly easy. It all worked out OK......

 

[rattler50]

They call me "MagGyver" at the shop for a reason......... :histerica

 

[CharlieVT]

My puller was a little too thick to get in the slot under the bearing but when I tightened it, the bearing came up and as I tightened it some more, the bearing popped off quite easily. I pressed the bearing back of after a little heat and it almost fell on. I heated the housing and it fell in. Without a heat gun it would be impossible. All in all it was fairly easy. It all worked out OK......

Good work!
Yes, I had to grind my three point bearing puller so the jaws would fit into the narrow space between the outer bearing race and the crown wheel.

Temperature differences make all the difference. When I have put the bearing in the oven and the crown wheel in the freezer, the bearing will drop onto the crown wheel. No press required, gravity does it.

Curious, how did you measure the preload for shimming your new bearing?