Loose yokes on my transfer case.

Both my yokes on my transfer case (231) seem to have some play. I get some vibes at high speeds and rotating clunks at low speeds. I have two brand new drive shafts in and my pinion angles are pretty much dead on. How can I tighten them up? Is it common for the nut to come loose, or more than likely it's internal?

Take the driveshaft off, and move the yoke with a finger on the shaft. If just the yoke is moving, the nut needs to be torqued. If both the yoke and the shaft move, you've got some bearing issues. You might be able to do this with the driveshaft installed if you can physically see the nut/shaft move.

Hope that helps.

It seems like they're is play in the CV itself. These are brand new drive shafts!

I have had issues with my rear SYE yoke loosening up, I have the Advance Adapters. The last time i tightened it I also "staked" it with a center punch in 2 places so it would not back off again.

This may be your issue, also check the center ball in the CV for issues.