if u think its a tranny issue, warm the car up to operating temps and WHILE the car is running, pull the red tranny dipstick, wipe off the fluid then stick it back in and wait 2-3 seconds then pull it out again. Now where is the fluid level at? Also what color is the trans fluid as well as if it smells burnt or not.
edit- is the sound coming from the motor or from the transmission? try to narrow down where the sound is coming from if u can.