weird noise

[csdmatt2005]

just the other day driving home form work i went to pass someone and a weird noise came from the rear. its hard to explain the noise buts its not a screeching but not a grinding either almost a little deeper than somone running there fingers down a chalkboard. it no does it only when i give it a lot of gas or passing someone and it does it more below 50 mph doesnt do it after 50mph. i can fix whatever it is but id like to get some help if anyone knows what it is so i dont go replacing every part lol. when it does it the engine downshifts normal but makes that noise and when it gets ready to go into the next gear it doesnt for like a secong but it keeps accelrating but the rpms stay up at the point where it usualy shifts at. the fluid in the tranny has been replaced hoping that it would fic it but it didnt and the fluid in the axle hasnt been replaced but is still full. any help would be appreciated

 

[csdmatt2005]

oh yeah the rpms go back down to when the noise goes away which all together only last for a sec or two