Very Weird Throwout Problem/Noise

[29 Tudor]

This one sure stumped me... I have a '29 Tudor. When the engine/transmission was cold or warm, no noise. After the transmission got a bit warmer, there would be a very strange screeching or "whining" sound coming from the throwout bearing whenever the clutch was depressed. I removed the inspection cover and when cold, you could rotate the throwout bearing and it felt absolutely perfect. After it got hot, you could occasionally feel a "catch" in it.

Today I pulled the tranny (pulled the rear axle) and got to the throwout bearing. For those of you that wondered, the left picture is what the inside of the throwout bearing looks like. I was expecting to find a bad ball or separator but no luck. It looked pristine!

The next picture shows what I found on closer inspection... see the shiny spot on the brass colored ring? If you look at the collar, you can see where it was rubbing. Apparently when it got hot, it started rubbing on the collar a bit and caused the noise.

Now here's the question: I measured the ID of the brass ring area and it is only .010 larger than the matching area of the collar which means there is only .005 clearance. I am thinking of chucking the collar in the lathe and cutting a few thousands off of it to assure plenty of clearance.... any thoughts? I believe the only purpose of the brass rings is to "seal" the front of the bearing to the collar so greasing the collar will force grease up into the bearing.

By the way, with this bearing, ( a BCA) there WAS a path from the grease holes in the collar into the bearing. I don't know if some of the new ones are truly sealed but this one wasn't. I'm sure it was replaced when the running gear was rebuilt (not by me) some years ago.

Of course, the normal project creep has grabbed me and I pulled the tranny apart to inspect it. The cluster has a number of badly pitted teeth and the other two gears show some signs of damage as well so I'll be ordering all new (USA) gears and rebuilding that as well.

Any thoughts or comments on the bearing/collar?

Thanks,

Steve

[Kurt in NJ]

You should check the pilot bearing too

Is there any spot on the hub that looks worn in one spot or is it the same all the way around?

[29 Tudor]

I put in a new pilot bearing today. The old one was fine but I'm not planning to go back in there. The wear on the hub is just on the bottom as shown in the picture. It's very slight but it has definitely been rubbing. I'm sure that was the "catch" I could feel in the throwout bearing when it was warm.

sd

[700rpm]

Talk to your supplier before you order your gears. Recent Mark gears have in some cases shown more slop than those of even a year ago. Snyder's is checking into the why.

[29 Tudor]

Thanks. Looking at Mac's and Brattons. Both say US gears.

[29 Tudor]

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I know how I appreciate it when someone tells "the rest of the story" in a thread so in that vein, here's the latest.

The old throwout bearing (BCA 2065-16) had a pair of brass rings that were only .010 larger than the diameter of the hub, giving .005 clearance from the bearing to the collar. That's what was rubbing and making the noise. The new bearing (National 2065-16) does NOT have the rings and in fact, is 2.125 compared to 2.070 for the old bearing in that dimension. In addition, the new bearing has much less of a gap (for grease?) between the fixed and the rotating part of the bearing.

It looks to me like the BCA bearing is designed to accept grease from the fitting on the hub while the new bearing is obviously not designed to be greased.

Hopefully this will help someone in the future.

Steve