when I turn the front driveshaft back and forth the axle has a lot of slack in it, before it turns the wheels and it grinds.  there is so much slack in it, when I am driving, the truck starts to buck back and forth, until I hold the clutch in.

Are you sure you have the same gear ratio in the fron and rear?

If there is slack between the drive shaft and the tires starting to move , more than say 1/2" or so the backlash could be off or the spider gears could be worn out.

A grinding noise isn't good.

Sounds like it is time to take it apart and start looking for the problem.

Start with the easy stuff and work your way in. Brakes axles then 3rd.