hey guys..just a question from a nubbie...ive noticed over the last couple weeks that when im changing gears and release the clutch and press down on the accelerator, i can hear a clicking noise from the rear of the car..i have a 1990 Gts-T with about 88k...theres also a little seepage on the tranni too...im not sure whether the knocking is the tail shaft or the diff...should i replace all the oils with some synthetic and clean it up and see if i can spot anything?..or should i get it looked at??