89 240 automatic, rear diff is pretty wet and a very high pitch noise comes and goes.bearing? anyway not familare w/ everthing back there. Is it a major job to change the gasket and bearing?

 

The front diff seal and bearing is a pain in the A**. I would leave that to someone that knows how to do it.
If you have the Torque off a little bit it could come loose or the total opposite seize up.

That is one thing I don't like doing at all.