1996 Pontiac Sunfire

Transmission problem
1996 Pontiac Sunfire 4 cyl Front Wheel Drive Automatic 150000 miles

at first you could here it sometimes, during acceleration. Eventually every take off you can here it now, unless you accelerate VERY slow. Ive put the front tires in the air and got under while I had some one put it gear, and the engine moved quite a bit.(In my opinion)my mechanic friend heard it by standing next to my car and said change the half shaft or axle. Didnt fix my problem. Last atf change I found some metal shavings or fragments in the oil pan. A couple of times out of no where iwas reversing very slow and the car grinded and stopped by itself when I shifted from R to N? ( It looked like if I had put it in P while reversing ) it sounded like my tranny had fell apart on the ground. I stopped driving it for a few days and I guess it fixed itself. So thats some history and my? Iis what could be the problem?
January 10, 2010.

If the noise is only while in first gear, planetary/bearings are probably on their way out.
Meaning rebuild time. Metal shaving in the pan also lead to this.

If the noise comes back, use a stethescope to narrow down the source.