Turning is shaky
 

I have a 1978 ford F150 and have replaced the tie rods, drag link, and rear brakes. Each seems to have helped but when I turn sharply and back up and turn the rear wheels seem to be skidding instead of rolling free. The front end seems to feel pretty good now but I need help figuring out the rear wheels. Any suggestions?

Do you know if the truck has a posi rear? If so, it may just require some of the lubricant modifier to help eliminate that.

I think it is. I have the rear tires up on ramps so I cant spin them. Everything I found on draining said to remove the rear cover plate. This one doesnt have a rear cover plate so I unbolted the cover plate on the front but cant get the cover to come all the way off. Is there a trick?