I'm not sure if I am following you 100%...

Unlike a car u-joint, there are no bolt on caps for these u-joints. You have to remove a clip on the inside edge of the U for each caps, and then drive then out.

After thinking about it more, maybe you are referring to removing the shafts from the tractor. There should be a bolt for the joint for the one on the side of the block. You can unbolt the other end to get the shaft out of the tractor in order to get the u-joint out to where you can work on it. There should also be one at the steering column end of the u joint that goes down to the block. 

I found this video on you-tube that shows the principle of driving out the caps. The biggest difference is clips are on the inside, shaped like a C in a groove.

<!-- m --><a class="postlink" href="http://www.youtube.com/watch?v=1d6v7zmM_WQ">http://www.youtube.com/watch?v=1d6v7zmM_WQ</a><!-- m -->

There are other videos on there as well.  Hope this helps.