My 90 model has 1/4 to 1/2 inch of slack on each tire/axle. when it is on jackstands you can pull the tires out that far. They do not move up and down as to there is no bearing slack only from in the chunck I guess. Any ideas on what is wrong?

 

Does the rear end have the Trac-Loc differential? If so you may have wear to clutch disks or side gears or the differential case. Also check the C-clip holding the axles in the side gears for wear. Some end play in the axle shafts is normal 1/2" is too much. The Ford spec is .03" but most axles are over that with no problems.