I forgot to mention also that when we came to a stop today after test driving, the car was in neutal but the driveshaft was making a banging noise. I got under the car and sure enough the driveshaft looked like it was trying to engage the rear end but was just hitting it. I had my wife put in park and it continued to do it there as well. It also got slightly louder as she stepped on the gas.
Think this has anything to do with the sputtering and dying problem?? I does shift somewhat firmly but doesn't seem too bad. Also, when it starts to sputter it won't shift up or down at all.

Thanks again,
Brandon Oswald