My girlfriend has a automatic 2008 Chevy cobalt 2.4l with 45k miles on it. She just got it from the dealership about 3 days ago. When she first tried it out it felt great, today though we noticed some issues. When she is driving at a steady speed the RPMs would all of a sudden go up and down on its own and you can feel the car jolting while doing it. It's not at high speeds like 90mph it's at 40mph were RPMs are at 2. She has a engine and transmission warranty, she called the salesman and he told her to come in tomorrow to have them check, but I would like some knowledge going in before hearing them say "nothing wrong".

Any ideas?

 

Sounds like its slipping in and out of overdrive. Check fluid and condition. If they dont know how take it somewhere else. They are sealed but can leak/ lose small amounts from axle seals. If its clean and full get a scan tool on it and check if torque converter is locking up at 40-50 mph. They should be able to go from there. I am a tech, hope that helps a little good luck.

 

This ^. The jolting definitely sounds like the trans slipping in and out of O/D

 

Went to dealership today and they told us that the torque converter screen was dirty and something else I forget. They got the car close to their closing time so they have it there over night to fix it but have us a rental for time being. Thanks alot guys! Hope this is the fix for issue!