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Old 12-30-2008, 08:49 AM   #1
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Default Universal joint rebuild?

Were these ever meant to be rebuilt? They sure don't last very long!


Mine have all of the slop around the pins on the outside where you can see the pins if that makes sense. THe center block where the small pin goes through the large pin is still tight and the only thing that holds it together still. I can see reaming out all of the holes including the one in the center block that holds it all together and using pins that are bigger but you can't really do that more than once.
Mine were not new to me. Why do the holes go out of round and wear if they are pressed in tight from the factory? How tight are they new?
Wanted to know if I am missing something that's not obvious to me...
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Old 12-30-2008, 09:39 AM   #2
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Hudy and Innovative Designs both make tools to replace drive pins.
Of course, the pins should be replaced before the uni holes are worn out.

The uni's wear from constant acceleration and braking. The pin - hole tolerance is very tight new. If you try to replace a pin without the tool you will see just how tight the tolerance is.
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Old 12-30-2008, 09:49 AM   #3
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I'm familiar with replacing the pins on the dogbone ends and have done that on all of the shafts on my buggy with only dogbones. Those, the pins wear flat spots against the drive cups.
My front uses uni's on the steering knuckles and seemed to wear different. The pin still looks round but the outer holes they go in are ovaled real bad. If I press the pins out I don't expect to see any wear on the pin from what I can see at the end of the pin. Maybe I will have to go ahead and take one out to verify. I wish the pins wore first then the other pieces. At this point it seems like the other way around - unless that is the point you are trying to make. That I will find the pins and the holes are both worn and I've neglected them. Don't have experience with these

If this is true I could overhaul them and put bigger pins in some reamed out fresh holes that are round again and keep a better eye on them. Not sure what happened yet and looking for some more advice before I screw them up...
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Old 12-30-2008, 10:31 AM   #4
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I just caught on to one important thing I missed while staring at these things. The pin cannot be a press fit at the ends of the pin or the uni's won't pivot at all. D'oh.
Maybe these aren't as worn as I thought. They still are pretty worn though. I'll have to rethink how I could make them better. It makes more sense how they wear so bad and quick now
Give me any ideas so I don't have to put them back in so sloppy. The only problem with leaving them is that they will get worse and eventually break. The way I see the design now there is no way that they could really wear any slower. There has to be a tight but moveable fit for them to pivot.
Makes the plain old dogbones look like lower maintenance!
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Old 12-30-2008, 10:40 AM   #5
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I am running Kyosho unis on my Cen Matrix buggy. Mine also show signs of wear and they are developing some slop. I was told that Kyosho unis and CVDs cannot be rebuilt. I know that the Mugen Unis and CVDs are rebuildable.
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