Rep Power: 208

i have a slight "tweeting" noise that happens when in reverse only (auto tranny),

its cold here around this time of year anywhere from 0F-30F most of the time,

i start the car in the morning to warm it up for about 5 mins, everything is fine, no noises,

as soon as i shift into reverse gear (even while still, not moving) i get a very faint occassional "tweeting" noise like a mouse or bird would make,

when i shift back into park, the noise stops, and the noise is not present while i am driving in "D" gear....only reverse,

any ideas?

 
Rep Power: 221

reverse gears are straight cut as opposed to being helical cut on the forward gears. This makes them much noisier by nature. check your trans fluid? may be low or dirty?

but if its happening even while still, maybe its belt/pulley squeak from the the extra load on the engine from being in reverse? (reverse is a very "low" gear)

hope this helps

 
Rep Power: 517

Heat shields squeaking? Could be dang near anything....
Get it acting up, set the handbrake hard so the car can't run away, and push/pull/move/stethoscope/tube/screwdriver it?