I think thta I may be afraid of an answer....bur need one, please.

On the lift, my left rear wheel on moves a small way toward the diff....but the right rear moves more than an inch inward, when I move the tire at the 12/6 position.

I don't know enough about differentials to guess...but this doesn't sound great!

Thanks for any help!

Are you saying the axle shaft itself is moving that much, or just the tire/wheel? If the axle shaft & diff yoke is moving that much, your yoke is completely worn out, and there may possibly be other worn/damaged parts inside the diff. If, however, it is JUST the tire/wheel moving, then you may have a worn wheel/hub bearing, which, while still not good, is far less expensive.