Yesterday I took my car out for a spin we went out to a stop sign and reved it up then hit L gear the worked fine. Then i go home and parked the car. THen when i get back in it i start the engine and every thing seems good. Then when i shifted into D some thing made a loud bang, then like 10 feet forward I lost more than 50% of the power on 1St Gear. The car wont move much. So I put it in L and it worked fine. Im thinking my tranny is about to die on me. What could be the problem?