There are a couple of bushings on the rear axle that can make noise but I would be looking at your kick down solenoid on top of your transmission. This solenoid controls modulator pressure and the control rod attached to it needs to be able to move freely.
Without starting your engine, turn your ignition on and then press your gas pedal right to the floor. You should hear a loud click as the linkage is pushed forward. If you don't hear anything check to see if you have power going to the switch. If you have power and the linkage isn't moving the solenoid is probably seized up. It can be removed and freed up.