373 rear end play?

I seem to have a lot of play in my rear-end (boy, that really sounds like fun!)

I get a bump when letting of the throttle on the highway. I thought it may be the U-joints, but found I can turn the driveshaft with my hand to about 1 or 2 o'clock with the brakes on. Is this much play normal? Is there an adjustment or tension setting in the differential? Or, does this mean I need new gears?

Any suggestions?

Some Play is normal, the best thing to do is take the cover off of the diff and look at the gears for any chipping or pits, I am in the process right now of redoing the seals and brakes in my truck.