help me figure out this transmission noise video

hello everyone i have an 01 mustang v6 i just swapped a used transmission in for mine, and i have this loud squealing noise when i first the car in reverse and when i and in first gear and really step on the gas, if you could let me know what this noise is, and if im going to have to take it out again


[yt]yUbNijbJUv8[/yt]


<iframe width="420" height="315" src="http://www.youtube.com/embed/yUbNijbJUv8" frameborder="0" allowfullscreen></iframe>


thanks for any help