Throwout bearing refurb?

[hikerjohnson]

So while chasing down a dribble coming from my neutral switch (now hopefully cured, at least for a seaon or two), I decided to clean up and re-grease my clutch throw-out bearing, when I noticed some spalling on the surface.



Woohoo! I'm a member of the exclusive JB Weld Club!







So there is the spalling on the bearing races, and I have some small spalling on the roller bearing itself - no pic of that, camera just wouldn't focus that close.

My question is two-fold:

First, should I care, or do they all do this, since the roller bearings just kinda "skid" anyways, being radial, and not tapered needles?

Second, I am thinking about putting these on a stone and just cleaning up the surface some and taking up the difference in my clutch adjustment. Are these little buggers hardened? I don't want to take off some hardened surface and then have the races /really/ wear out.

Since its almost a hundred dollars to replace all three items, I'm wavering on doing anything at all, or perhaps just buying a new needle race.

[disston]

I would replace those. Anything beyond a slight color change is no good. Those thrust pieces are pitted.

This is a wear item. I believe in changing the bearing before it gets bad enough to cause damage to the thrust pieces but this is hard to gauge. You are lucky you don't have to buy a new rear trans cover. Consider a hundred bucks this time a cheap repair compared to what it could have been.

[Plaka]

Originally Posted by hikerjohnson

So while chasing down a dribble coming from my neutral switch (now hopefully cured, at least for a seaon or two), I decided to clean up and re-grease my clutch throw-out bearing, when I noticed some spalling on the surface.



Woohoo! I'm a member of the exclusive JB Weld Club!







So there is the spalling on the bearing races, and I have some small spalling on the roller bearing itself - no pic of that, camera just wouldn't focus that close.

My question is two-fold:

First, should I care, or do they all do this, since the roller bearings just kinda "skid" anyways, being radial, and not tapered needles?

Second, I am thinking about putting these on a stone and just cleaning up the surface some and taking up the difference in my clutch adjustment. Are these little buggers hardened? I don't want to take off some hardened surface and then have the races /really/ wear out.

Since its almost a hundred dollars to replace all three items, I'm wavering on doing anything at all, or perhaps just buying a new needle race.

To fix the races they have to be ground, chromed and ground again. You don't have the gear. if you stone them you won't get the flatness and parrallelism a bearing needs. The bearing itself cannot be fixed. Put it together with some good moly grease and save up for a new one. Maybe call around and see if a good used one can be had. Don't let it get to point of frying.

I don't have mine apart at the moment (gimme a couple days) so I can't measure and see if they are tapered. If they are, they don't "skid". From the pics of the races they look flat so strait rollers.

Don't hold the clutch in any more than you have to. Get it to neutral and idle there.

[daveoneshot]

It's good to hear someone else putting their Airhead into neutral and letting it idle until ready to go. I do it all the time at red lights and situations where I have to wait for things to get going.

[hikerjohnson]

Well, here's the thing. I can't find any evidence these are hardened, and in fact, it almost looks like the smaller race is sintered; and there is no chrome at all, just something like a parkerized coating.

Overall it's a pretty odd setup.

I've spec'd bearings for a few jobs in the past, and never in my wildest imagination would I call out a plain roller bearing to do thrust duty like this, even when the load is light. There is no taper on these races.

Since these are pretty obviously pooched, I will experiment with cleaning up the surface and see what I can come up with. If you look closely at the pictures, you can see that even the factory finish on the raceway areas was pretty poor.

[Pokie]

I'd lube it and put it back in until I could find another one. I wouldn't bother with anything fancy to lube it with before putting it back as it will likely get flushed out with transmission oil. This sort of damage usually happens when some water gets in there and can't get back out (storage with dirty or contaminated oil is pretty common). There is a rubber seal on the outside thrust piece that wears out but never get's replaced until it starts to make a mess on the back of the transmission. Before the oily mess is noticed, it can also allow water to get in.

If you run across someone that does a lot of work on older BMWs, they will likely have these parts in their stash. Replace all three pieces as well as the seal on the thrust piece.

Like in the MSF course, don't sit idling in neutral unless you are protected.

[Plaka]

Originally Posted by hikerjohnson

Well, here's the thing. I can't find any evidence these are hardened, and in fact, it almost looks like the smaller race is sintered; and there is no chrome at all, just something like a parkerized coating.

Overall it's a pretty odd setup.

I've spec'd bearings for a few jobs in the past, and never in my wildest imagination would I call out a plain roller bearing to do thrust duty like this, even when the load is light. There is no taper on these races.

Since these are pretty obviously pooched, I will experiment with cleaning up the surface and see what I can come up with. If you look closely at the pictures, you can see that even the factory finish on the raceway areas was pretty poor.

Plate and grind is how you fix them. I wouldn't expect them to be plated originally.

The idea is the bearing is only loaded briefly and spends most of it's life unloaded---unless you sit with the clutch in waiting for a light or something.

If you screw up the bore in the transmission housing, it gets costly.

There have been many variations of that assembly over the years. You wouldn't think it's so hard? BMWs style is to overbuild/understress. But they blow it here and there.

[disston]

It is a poor design. Either a tapered roller or a ball bearing design (like the /5) would be better. There is no known substitute that I have ever heard of.

This design changes with the flex plate change in '81. So it is used for only 7 years.

[bmwrench]

I wouldn't call it a poor design. I doubt that I've replaced five of them in the years I've worked on BMWs.

[craydds]

Originally Posted by disston

There is no known substitute that I have ever heard of.

There is a thrust "bearing" made of teflon, it's like a teflon flat washer sandwich, that has been used in place of a roller bearing. I just installed them in place of the old swingarm thrust bearings (similar to the BMW throwout bearing) that were rusted in an old dirt bike that I'm rebuilding. Should work well in the swingarm, but I don't know if something like that would work for the clutch throwout bearing, nor have I ever seen anything like it, either. One would have to custom make it, then it would be an experiment.

[Plaka]

Originally Posted by disston

It is a poor design. Either a tapered roller or a ball bearing design (like the /5) would be better. There is no known substitute that I have ever heard of.

This design changes with the flex plate change in '81. So it is used for only 7 years.

You could go to a bearing house and get a replacement, in all likelihood. Some modifying of other parts may be required for fit. Takes a lot of combing through catalogs. A Thomas Register and/or Sweets is real handy.

[disston]

Originally Posted by Plaka

You could go to a bearing house and get a replacement, in all likelihood. Some modifying of other parts may be required for fit. Takes a lot of combing through catalogs. A Thomas Register and/or Sweets is real handy.

I doubt there is any other bearing that fits. This is another of those "proprietary" part things, I'm sure. But according to the measurements of early and late bearings in 5 speed on Anton's Web Pages there may be a way to modify the cover to accept the late model set up. I think Anton is checking this out but haven't heard about any progress from him.

[Plaka]

Originally Posted by disston

I doubt there is any other bearing that fits. This is another of those "proprietary" part things, I'm sure. But according to the measurements of early and late bearings in 5 speed on Anton's Web Pages there may be a way to modify the cover to accept the late model set up. I think Anton is checking this out but haven't heard about any progress from him.

Having proprietary bearings made is extremely expensive. This makes it unlikely. But that doesn't mean it's anything common. In any event, you don't want another of what just failed. You might buy a more costly bearing, that will last.

The last time I bought a flat radial bearing (about 2 1/2") it was like $25. It was for the top of a studio tripod that had no bearing, and was suffering for it. A little machining and it went right in.

[hikerjohnson]

Well, I took the pitted faces to some 400grit on a surface plate, followed by some quality time on emery cloth, and I have got a better surface finish than the factory ever put on, at the expense of maybe a grand total of 30thou of thickness lost. If I'd been a little more ambitious, I could have made them actual mirrors, but I feel like a tiny bit of "tooth" will help keep some lubrication there.

These parts were NOT hardened, and were in fact pretty damn soft.

I did drop the 30 bucks on a new bearing since the old one was pretty pitted on the rollers; between the two, I suppose I ought to be good for another 35 years, give or take a decade...

BTW, some modest searching yielded no immediately compatible bearings, but I didn't try very hard. In my limited experience, the local bearing houses are not interested in ordering in strange things for me, and BMW had it on the shelf ten miles down the road. Eventually, despite my best efforts, time does become worth money, at least for the weird stuff like BMW bearings.

[disston]

I will try to convince you one more time. After this if you want to spend your time looking then be my guest. But there is no substitute "other" bearing available. The throw out bearing of needle design on the 5 speed from 1974 till 1980 is not a standard bearing size. It is a proprietary bearing.

Good luck with the repair. I think it should work. But let us know if this goes out prematurely, like anything less than 20 years?