noise while in gear at idle

[keithyota]

263k miles. just started making a noise, like a sqeel. seems to go away when driving or can't hear it then. Only occurs when in gear.

ideas?

 

[pluton]

What year, what model, what trans?

 

[keithyota]

1999 SR5 4wed, corrosion belt... 22R. tranny not sure...