'08 Chevy Impala Hard Shifting

Pardon me if this is a common question.
My '08 Chevy Impala (116,000 miles) has had a recurring issue over the past few months. After I have first started it, and for maybe the first 15 minutes it is running, it has been ‘shifting hard’ from 1st to 2nd gear. Basically, the engine revs much higher than it normally would and it ‘thunks’ into second gear. If I intentionally push the gas slower it does not happen. The guys who service my car (not Chevy) told me that my Transmission fluid level is fine. Any thoughts?

Have a tranny specialist look at it?

Oh, and fin dan independantly owned and operated shop of you can. Avoid chains.

Sounds like a plan, Mountainbike. I used to have such a good shop when I lived in Massachusetts… not so now that I’m in Ohio.