Diagram of rear suspension

SOURCE: drivers rear wheel leaning in

Strut bolts could be loose or you could have a bad bearing.

SOURCE: f 150 4x4

I would suggest to swap the rear tires to the front and see if that helps.
It could also have a shock absorbers problem as well.

SOURCE: vehicle shaking like it is missing real bad

when was the last tune up done and fuel filter was changed?
there is no spark plug wires I had to replace the boot for the number one cylinder on a 2000 expedition that was also having the same problem if the check engine light is on take it to auto zone and they will put it on a tester free of charge and I hope and pray that it is not the problem like the one I am working on right now I am replacing the upper and lower intake gaskets

SOURCE: 1968 Ford Mustang Fastback, left rear side leans

No, likely springs

SOURCE: the rear driver side wheel

You did not indicate which Model vehicle this is. In general, a car with front-wheel drive has rear wheels which are Independent of each other. This means there is no solid axle going from one side of the car to the other.

The Independent rear wheel is mounted to a strut. The strut assembly is adjustable and gets an Alignment just like the front-end parts do. It must be put on an Alignment machine. Another area which can tilt a rear wheel is a severely worn spindle or wheel bearing.

This would mean the rear strut may be properly in place, but the spindle and bearing inside the rear brake drum or rotor has too much play and is allowing the wheel to tilt. You would hear a loud grinding noise if the bearing is bad.

I do not want you to ignore getting your car checked, but a complete answer includes vehicles which have the rear wheel construction built to allow for the rear wheels to flex in and out depending on terrain and load. These would be the cars where if you jacked them up, the rear wheels would not come down straight. It takes a few miles before the parts level out.

You should take the weight off the one wheel and see if there is play anywhere. The struts can be shimmed and the shims may have fallen out. You may have a rusted strut tower. Once you assure yourself the car is safe to drive for Alignment, thats the next step.

Thanks for using Fixya. I hope my solution is very helpful to you.