In my '95 gt mustang convertible when i start driving and it shifts to second (auto tranny) the car rumbles pretty heavily. and it's right under me so i know it's the transmission. I work for a master tech mechanic full time and he drove it and told me that it feels like clutch chatter. has anyone else had this problem and if so do i need a rebuild? he told me that there's a chance that a transmission service (fluid, filter etc.) may fix the problem. I just really want to know is there anyone that can pinpoint this problem? It's only when it shifts to second and my RPMs are low. if i give it gas or let off the gas completely, it will stop. the shifts are NOT rough either, they are smooth shifts it's just an incredible rumble/shaking.