Fluid level in diff can't cause anything like this. The fluid level in tranny / torque converter can. I'd replace the fluid in tranny several times to make sure the fluid is as new as possible and refill it to the correct level (to check level you must level the car, warm up the tranny up to ~35C and check the level through the fill hole while motor is running). Your symptoms are very similar to low fluid level issue. Even jacking trick can be explained - you force the fluid to go to the pump and to to the torque converter.
Last edited by Nervous; 11-27-2012 at 10:37 AM.