I have a 2001 Dodge Neon, 4cyl. and it keeps slippin. It started about 2 weeks ago and it wasn't that bad but obvious. I had my husband's brother come look at it and he suggested that I put some transmission fluid in it because it was low, so I did and it was still slippin but it only slipped when I had it in drive with my foot on the brake.So my step dad said I needed the air filter changed so I went ahead and took it to wal-mart to get the full service deal, and they changed it and filled up the oil stuff. Well when I got the car back it was worse. Now it slips constantly like jerking . It doesn't do it when I am driving but only when it's in reverse and also when I'm at a stop light like in drive with my foot on the brake. When I put it in park it stops but every now and then it will slip a little in park, WHAT IS WRONG? Help!!