1998 OD 4 spd caravan 3,.0 tranny question

From : chevrolet

Q: 2001 dakota slt 4x4 its developed this little squeak like something needs oil when backing. its not the brakes or brake warning i think since the noise isnt happening when i apply the brakes. generally it squeaks once like a door opening squeeee then stops. it may be related to turning sharply as i only notice the squeak when backing out of the carport. its coming from the back end somewhere. its not very loud i only hear it when ive got the window rolled down. ive tried the brake setting procedures driving forward/back and braking sharply but no change. is this just one of those sounds older trucks pick up over time or something that should be investigated what might it be jmc .