I bought a 05 trailblazer Lt with about 223K miles for $401 at a auction and got it running. Drove down the rode and shifted fine till it hit 3rd gear and it was bouncing off the rev limiter. Checked the trans fluid and it was full. It was dark but did not smell burnt. The check engine light also comes on trying to go into 3rd. What all could cause it to do that? Will I need a new transmission?