1990 toyota pickup, squeaks when i accelerate in gear, goes away if i take it out of gear and rev it. i think its a u-joint or something in the differential because the noise is coming from the rear end, any ideas?

Sounds like a bad throw out bearing.

Disconnect the stabilizer end links & see if it goes away

Then disconnect the bottom of the shocks

You've a gear box problem.
Stop the car and repair it or substitute for a rebuild one (much cheaper).

I think what happened was the cv joint got pulled out of the slot. go underneath the car the push it back in.

It's an automatic. 207,000 miles on the engine.

I'd check the U-joints first. Then, check for low gear oil level in the gear box.
Also examine it by draining the gear oil to see if it has any metal fragments in it.
If it does, you probably have a bad bearing or something else coming apart.

its a wheel bearing. .will need to be inspected to determine the correct one. Also tires could also do this if the steel seperated internally. Rotate the suspected tire to see if it follows the tire.

If it seems to run well otherwise, you might have a partially obstructed catalytic convertor. Usually if this is the problem, the engine will also bog down even if you try to rev it up when it is in neutral.

sound like your clutch is slipping.

sound like a vacume leak get a can of carb cleaner . with the engine idling spray around the intake and base gaskets if the idle changes you found your leak cure the leak cure your problem