What are some of the symptoms of a dying box? This is in a '93 YJ that has seen off-road for years. Turning 33" and then 38.5" swampers. Anything I can do to the box to see if needs a rebuild?

I would recommend NOT trying to rebuild a PS box. I've had a couple of friends try it and say they would have been better off just getting another one.

I personally use $15 junkyard ones which seem to last about 5 years each.

My last saginaw box felt like there was a chunk of something getting stuck in the gears inside of it as you turned it...yikes!
Of course, 5 years of hard wheelin with 36s and 35s tend to do that kind of thing to steering boxes. <IMG SRC="smilies/biggrin.gif" border="0">

I had one that would all of the sudden jerk to one side or the other while going straight down the road. It was usually to the right but some times to the left.