Purchased an 02 impala that was sitting for about 5 years. After getting it running again (runs well) it barely moves forward or backwards. I'm suspecting a bad trans, however I would love feedback from others more knowledgeable. I come from an auto background, but needless to say, there's a reason why there are specific mechanics who service transmissions. (I don't know anything about them!) check engine light comes on for some type of gear mismatch code if I remember correctly. Can simply sitting cause a trans to go bad? I CAN get it to move and drive and even shift gears once I get it moving, but getting it moving requires revving the crap out of it and eventually it will lurch forward and start moving. Any ideas on how to bring it back if possible?