hey guys. a few months ago i had to get a new transmission in my 08 wrx. i had already rebuilt the original, and it went out again....somehow lost fluid. a shop had replaced an axle not a month before this happened. anyway. bought a used trans and rear diff from a reputable friend in the subie community. well, since then it has developed a really weird and frustrating vibration. the vibration is present in first gear, but is most noticeable in second gear under strong torque. i'm only running "cobb stage 2 + SF", so i dont think i have enough hp to shift the diff that much. i recently bought some whiteline bushings (not installed yet) and am also going to get motor and trans mounts soon, as well as the sub frame bushings. can anyone think of anything else it could be? possibly something in the trans or diff? a busted pin, broken bearing? (i do not know much in this realm of cars.) any help would be appreciated. thanks.