Putting cv joints together - problem

I had to take two brand new cvjs apart to do some machining, and am having a problem putting one back together.

I know that the inner star and the cage both have a right way round, and they're correct - compared to two old joints and the other new one which is re-assembled and working nicely. (For info there's a wider bevel on the edge of the cage that you can see when assembled, and the ball grooves in the star are closer to the shaft hole at the visible end).

The 'good' one went together as you'd expect, greasing everything a bit, assemble cage and star into the bell, putting one ball in, another in two slots away, next another two slots and then fill the gaps, all the time manipulating the joint round and round to bed everything, no force required.

The tricky one won't let me get a third ball in using the same method. The cage doesn't want to rotate with the star, but for any movement of the star will only easily move half of that. I've also tried putting the second ball in opposite the first, but still can't get a third in anywhere. On the good one the cage and star happily move together.

I may have used the balls, cage and star from one bell with the other, but that shouldn't make a difference with brand new joints. In case that assumption is wrong, I'm just going out to the workshop again to take the good one apart and swop them over in case.

Everything is extremely clean, but I'm going to wash the bad one and look for burrs in the cage before I try the swop over.

When I come back in, I expect someone to have told me where I may be going wrong. And I might swear.

So where were you all in my hour of need?

All done. I twigged as I took the good one apart again.

This shouldn't be a problem with a used cvj, but new ones have a very tight clearance between balls and cage.

With just a couple of balls in, it's possible to twist the star relative to the cage and the bell-shaped casing a little. Not so much that it's obvious, but enough to jam things up as you try and put a third in. Putting a half shaft (or similar tube) into the star and winding it round at various angles isn't enough to correct it if everything's greased - the balls stick in the cage slots. You need to grip half shaft and bell and rotate one against the other until the balls are centred in the cage slots and grooves.

For info, I did watch a GKN video of cvj assembly on a production line, and there didn't seem to be any choices made fitting parts together - they're confident that all cages fit all stars, bells and balls, so I was pretty sure that mixing components (on brand new) cvjs wasn't a problem. But I also now know enough to say that I would mark the three major components relative to each other, and each ball would go back into the same slot if I were doing a used one.