s13 ka24de whistling/whining troubleshoot

started noticing a whistling/whining sound while driving on the highway today. gets louder and started while on turns, during accel, and when on gear. it goes quiet when i kick it in neutral.

sounds like its coming from the rear but can’t be too sure might be tranny.

its a s13 hatch stock motor

might be bearings? but sound stops when out of gear so not too sure
low diff fluid?
or oil pump? found a long dent going horizontally across the middle of my oil pan the other day, no leaks though.

any other thoughts and suggestions?

It’s your fuel map, it’s got a nasty hole. That’s why you’re unloading in third.

Nos timing. Jesse told me.

Vaccum leak?

window seal isnt in right?
check trans fluid
buy a skidplate

does it still do it on corners while in neutral? sounds like a driveline issue. possibly tranny, diff, wheel bearing etc.

pinion bearings? possibly

sound stops whenever i clutch and whenever im in neutral even when revving. its starts lower pitch usually in 2nd gear and goes higher pitch as i accel. started sounding a rough a bit in 2nd and 3rd for like a minute, then went back to normal whistling.

could it be low trann/diff fluid? or throwout bearing?

kinda sounds like this
http://www.youtube.com/watch?v=K6VL9D6Y0Ik