I have an 04 PD, 27 kohler. Installed the updated reverse system, and ran it about 3 hours. Noticed after last run that if I hold the lower unit I can rotate the upper back and forth a bit, not much, but its real noticeable. I see the reverse pin moving as I do this and I don;t recall having this before, does anyone have play between the upper and lower like this?

There are 2 bushings inside the tower on the top and bottom. They get worn from not being greased regularly and in your case with it being a 2004 just being old. There is a chance if you didn't notice it before, if you add some grease to your tower it could take some slack out of it.

Theres not even 100 hrs on this motor, and all the grease fittings were pumped full. I will hit them again and see if it makes a difference. Kind of interesting it started after I installed the upgraded reverse pin system. Thanks for the input.

There will be a little movement, similar to lash in a differential.

You will have some play in the gears, but not much. One thing that you can do is loosen the bolt that half moon gear slides on enough so that you can wiggle the half moon gear. Push the half moon gear "inward" at an angle, so that it meshes tighter to the round reverse gear. Then tighten the piss out of the bolt to somewhat "lock it in place". This took out almost all my slack.