97 S-10 blazer front drive shaft

First question does the front drive shaft spin all the time. I have a vibration like a bad universal, replaced the rears and this helped. But the front seems to have some play in it as well.

Not in 2W.
Describe your vibration. at what mph and on pull or coast or steady speed.
Do you have the double piece drive shaft and the double u joints on it?
Did you keep shaft and joints timed up when replacing joints?
Best way to check for variation is to put jack stands under all 4 corners and run it threw the gears and in 4W and out of 4W.
Then remove tires and wheels and bolt rotors and drums back on and run it threw all speeds and gears and 4W and 2W and see where it vibrates the most and with tires on or off.
Post back what you find.