I have an '89 F-150 (5.0, 5 speed) which I bought new in '89.

A few weeks ago it started making a chirping sound (imagine a loud squeaky
bed spring) from under the truck all of a sudden.  That is, I drove it one
day no sound, next time I drove it I noticed the noise as soon as I began to
back up the driveway.  It was very noticable for a few days, then gradually
got much quieter when going forward, but is now quite loud in reverse.  It
makes this sound only when the clutch is released, pressing the clutch
peddle in makes the noise stop immediately.  And it seems to be a little
louder the more load there is (like when going up a hill).

The truck still has the original factory clutch, now with over 172,000
miles.  I really don't mind replacing it if that is what it needs, but the
funny thing is that the clutch feels as solid as ever and is no where near
slipping....

Before I just tear it apart I would rather be sure I am fixing the right
thing.

Has anyone else out there experienced a problem like this?  Does this sound
like it could be clutch related, or maybe a u-joint or something else???

Any input greatly appreciated,,

John