bolth sides have a quarter inch play when i check them like ball joints .could i tighten the big nut to see if the extra play goes away ? i nodiced my axle was leaking diff fluid . being that the unibearings are bad could this cause the axle shaft seal to go bad too ?

 

The hub nut does supply clamping pressure to retain the bearings in the hub, but one the hub shows movement it's time to replace it.

Tightening the hub nut just increases the torque on the nut (torque spec is 175 ft lbs) and increases the tension on the stub shaft.

Replace the hub.

 

would that cause the axle shaft seal to go bad ?

 

Dirt/mud in the tube.
Low oil level.
Pitted shaft.

etc.

 

Yes, a badly worn bearing could allow the wheel centerline to move above it's intended location slightly, pulling the axle out of alignment with the seal. Or the seal might just be worn out. Either way you need new bearings and seals.