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Discussion Starter #1
Went to change rear tire on 99LT 60000+ miles. When I took out the studs that hold the wheel on, oil ran out all five holes.Not just a little, almost the entire final drive reservoir. Had replaced the bearing 15000 miles ago, it looks and sounds good. The outer seal is fine....and no oil residue anywhere on the wheel etc.


Any idea what has happened? How to remedy?
 

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If you had oil out of the bolt holes removing the rear wheel bolts and you final drive is empty, the seal is NOT good. Did BMW replace the drive and was it less than two years ago? If so take it back to the dealer and have them replace the FD. There is not anyway that I know of for oil to leak out of the FD and it not be a seal issue. JM2CW
 

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bigpig said:
Went to change rear tire on 99LT 60000+ miles. When I took out the studs that hold the wheel on, oil ran out all five holes.Not just a little, almost the entire final drive reservoir. Had replaced the bearing 15000 miles ago, it looks and sounds good. The outer seal is fine....and no oil residue anywhere on the wheel etc.


Any idea what has happened? How to remedy?
You had too much oil in the final drive. I'm surprised that you didn't have other signs of too much oil such as oil being vented out the breather.

What to do: clean up the mess.
Install your rear wheel.
Fill the final drive with appropriate lubricant up to the bottom of the threads of the filler hole. Do not spin the wheel to get more oil in, just let the oil settle until the level is even with the bottom of the threads. More than that is too much.
(You may find upon removing the final drive filler plug that you still have a little too much oil if you have not drained oil via the drain plug. Oil running out the wheel bolt holes will bring the level close to the proper level, but you may still have a little too much. I suggest draining the final drive via the drain plug and then refilling to the correct level).
Reinstall oil filler plug.
Go for a nice long ride.
Don't worry.

Explanation: The crown wheel assembly (which includes the hub the rear wheel is bolted to) is drilled and tapped all the way through for the wheel bolts. If you have too much oil it will come out those holes when you remove the bolts just as you observed. I was surprised when I first observed that the rear wheel bolts were involved in keeping the oil inside the final drive, but that is the way it is.

Replacing the crownwheel seal will have no effect on this. If the drive was not leaking before you removed the rear wheel, there is nothing wrong with your seal.
 

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CharlieVT said:
Explanation: The crown wheel assembly (which includes the hub the rear wheel is bolted to) is drilled and tapped all the way through for the wheel bolts. .
Charlie I think you meant to say.
Only the center bolt hole is tapped all the way through.
 

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Discussion Starter #6
If you had oil out of the bolt holes removing the rear wheel bolts and you final drive is empty, the seal is NOT good. Did BMW replace the drive and was it less than two years ago? If so take it back to the dealer and have them replace the FD. There is not anyway that I know of for oil to leak out of the FD and it not be a seal issue.

According to the schematic, there is no seal other than the outer and inner housing seal. They have been replaced and there were no leaks around the housing. If you look in to the cluster (holes) from the wheel side you can see the ring gear moving and oil is present.
 

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Discussion Starter #7
My understanding of the seals are they are to keep the oil contained in the housing? Both seals are on the outer housing. Is there a internal seal that keeps the oil from leaking to the bolt holes?

I always drain the final with the drain plug, so I am at a loss on how I overfilled it....never have had any issues in the past.

Please keep the answers coming, I appreciate it!
 

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murray said:
Charlie I think you meant to say.
Only the center bolt hole is tapped all the way through.

Well, sort of but not exactly. To clarify: The outer holes do communicate with the inside of the FD housing (on at least some of the crownwheel hubs I have seen.) The outer portion of the bottom of the outer wheel bolt holes is bottomed in the body of the hub. The inner portion of the bottom of the outer wheel bolt holes is bottomed by the aluminum component of the crownwheel assembly. Note that crown wheel assembly is made up of two components, one carbon steel, the other aluminum, which are pressed together. This assembly comes from BMW as one part. And there is a small gap there that will let oil out. If you just sound the bottom of the outer holes you would conclude that they are solid at the bottom. But they are not.
 

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bigpig said:
My understanding of the seals are they are to keep the oil contained in the housing? Both seals are on the outer housing. Is there a internal seal that keeps the oil from leaking to the bolt holes?

I always drain the final with the drain plug, so I am at a loss on how I overfilled it....never have had any issues in the past.

Please keep the answers coming, I appreciate it!
In a little while I'm going to go pop open my spare FD and take a few pics. I'll reply more after that. Meanwhile, don't throw away your final drive. :histerica
 

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I am still learning here; my previous answer about too much oil was based on what I recalled of the machining of the crownwheel hub. So much for going on memory!
Now I am curious what the inside of your drive looks like.
Attached here are some pics of my spare which I just opened.

One pic shows the hub with bolt holes. I think you can see the bottom of the outer holes where the bottom is partly the metal of the carbon steel hub and partly the pressed in aluminum component of the crown wheel assembly. There is a small space at the bottom where the bolt hole communicates with the cavity inside the aluminum casting of the crown wheel assembly. If I shine a light down one of the four outer bolt holes, I can see the light through the center bolt hole; all the bolts hole communicate with the cavity in the center of the aluminum casting.

However, what I don't see on this particular assembly is how oil from the oil bath would get into this cavity inside the crownwheel assembly. This is why I wonder what your crownwheel assembly looks like. How did oil from the housing get inside the cavity of the crownwheel assembly I wonder?

It was reported in BMW Owner's News (Max Parkhouse's column IIRC) at least one case of FD failure where the aluminum component was not properly fitted to the crown wheel hub. This resulted is symptoms of final drive failure, not what you are reporting; but the report gets me wondering. It seems to me that the obvious conclusion is that there is a communication between the cavity inside the crownwheel assembly and the oil bath, but where it is, or if it is of any significance remains a question.

Why don't you open up the drive and have a look? And take some pictures.

You don't need to remove the final drive from the bike. Remove the brake caliper and rotor, then remove the final drive cover fasteners. Tap the cover off the final drive. The cover with the bearing, seal, and crownwheel assembly will come off. You will then be able to inspect the inboard end of the crownwheel assembly.
 

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Discussion Starter #11
Thanks for your help CharlieVT...

I have the final drive on the bench. I filled the unit to the edge of the filler hole. With in 20 minutes oil starts to seep from the bottom stud hole....go figure....
 

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You do have the old style FD with the drain plug at the very bottom of the housing? It should look like this only without the tan wiring. If so and you have been filling through the proper hole, check under your front rubber boot and see if it's full of oil. If so, check your transmission level. I suppose the rear tranny seal and the front FD seal could both be leaking, but I defer to Charlie. He is the FD guru. :bowdown:
 

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Discussion Starter #13
Posted too quick....my unit looks similar to the pictures. I will disassemble and report back
 

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bigpig said:
There seems to some end play between the aluminum and steel pieces. not very much but detectable. Everything is free and smooth.

No transmission leaks.....
You can detect play between the aluminum piece which carries the tapered roller bearing and the steel hub which consists of the hub with wheel bolt holes and the crown gear?!?

If so, that's not right. This is the unusual point of failure I referred to above and was described in BMW Owners News. The aluminum piece is an interference fit into the crown gear/hub part. If it is loose, that's a problem. The crownwheel assembly would need to be replaced IMO. And, if it is replaced gear lash between the pinion gear and crown wheel gear needs to be checked and adjusted by reshimming the tapered roller bearing.
Very interesting. I've never seen what you are describing. Only know of it from the BMWON article.

I am guessing that looseness between the aluminum part and crownwheel hub is where your oil is getting into the cavity in the hub.

Very interesting, but troublesome for you.

Let us know what you find....
 

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Discussion Starter #16 (Edited)
CharlieVT said:
You can detect play between the aluminum piece which carries the tapered roller bearing and the steel hub which consists of the hub with wheel bolt holes and the crown gear?!?

If so, that's not right. This is the unusual point of failure I referred to above and was described in BMW Owners News. The aluminum piece is an interference fit into the crown gear/hub part. If it is loose, that's a problem. The crownwheel assembly would need to be replaced IMO. And, if it is replaced gear lash between the pinion gear and crown wheel gear needs to be checked and adjusted by reshimming the tapered roller bearing.
Very interesting. I've never seen what you are describing. Only know of it from the BMWON article.

I am guessing that looseness between the aluminum part and crownwheel hub is where your oil is getting into the cavity in the hub.

Very interesting, but troublesome for you.

Let us know what you find....
Not good....you can hold the aluminum part and when you put it on the bench and then pick it up you hear and feel a distinct clunk....

Thanks for all your help....

I can send to you if would want to inspect it...(grin)
 

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bigpig said:
Not good....you can hold the aluminum part and when you put it on the bench and then pick it up you hear and feel a distinct clunk....

Thanks for all your help....

I can send to you if would want to inspect it...(grin)
Sure, I'd be happy to see it.... but for what purpose other than my own entertainment I don't know. ;)

Here's what I'd do to try and take the pieces apart for inspection:
Remove the bearings. Putting the whole crownwheel assembly in the oven at 250F will ease removal of bearings.
With the bearings off I'd heat the thing again. Also put a damp towel in the freezer.
After the thing gets to temp take it out of the oven, wrap the cold damp towel around the aluminum part and see if you can get the components apart. (You might not even need to cold towel, sometimes things come apart just by heating the whole thing up.)

It would be interesting to inspect the mating surfaces and measure to see what the interference is. I'm not sure what is should be but some of the mech engineers on this site might offer an opinion as to what the fit should be. If you get it apart, and the mating surfaces look okay, you might consider reassembly with a Loktite product specifically designed for that kind of application.
 

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Discussion Starter #18
CharlieVT said:
Sure, I'd be happy to see it.... but for what purpose other than my own entertainment I don't know. ;)

Here's what I'd do to try and take the pieces apart for inspection:
Remove the bearings. Putting the whole crownwheel assembly in the oven at 250F will ease removal of bearings.
With the bearings off I'd heat the thing again. Also put a damp towel in the freezer.
After the thing gets to temp take it out of the oven, wrap the cold damp towel around the aluminum part and see if you can get the components apart. (You might not even need to cold towel, sometimes things come apart just by heating the whole thing up.)

It would be interesting to inspect the mating surfaces and measure to see what the interference is. I'm not sure what is should be but some of the mech engineers on this site might offer an opinion as to what the fit should be. If you get it apart, and the mating surfaces look okay, you might consider reassembly with a Loktite product specifically designed for that kind of application.
One step ahead of you....tried the heating thing...no good, nothing seems to budge. However, now there is no movement. I'm not sure that is a good thing, because now the two pieces seem locked together. Running out of options....hotter heat....puller....sledge?

On your unit the aluminum and the steel stud hole piece DO move independently of each other...right?
 

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Ok, now you guys have gone and gotten me worried. I've had the rear wheel off twice - the first just after I got the bike (July 09) and had a new rear tire put on it and once in September to repair a flat. Both times I found a very light film of gear lube on the wheel bolts and between the wheel and the hub it bolts to. It has been 10K total miles since July, I've changed the oil in the FD twice - both times clean and no signs of metal in it. No noticeable drop in level, no play in the rear wheel and no visible signs of leakage with the wheel on and torqued down.
 

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rcoolbaugh said:
Ok, now you guys have gone and gotten me worried. I've had the rear wheel off twice - the first just after I got the bike (July 09) and had a new rear tire put on it and once in September to repair a flat. Both times I found a very light film of gear lube on the wheel bolts and between the wheel and the hub it bolts to. It has been 10K total miles since July, I've changed the oil in the FD twice - both times clean and no signs of metal in it. No noticeable drop in level, no play in the rear wheel and no visible signs of leakage with the wheel on and torqued down.
I would think you have nothing to worry about.....when I pulled the wheel the oil POURED out....<grin>
 
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