1997 Chrysler Concorde Transmission won't shift into overdr

Transmission problem
1997 Chrysler Concorde 6 cyl Automatic

I just had my engine replaced. The new engine has 52,000 miles on it. The old engine had 120,000 miles. The mechanic cleared out the computers' memories but the check engine light still came on. He said it was the speed sensor. He replaced those and the engine light still came on. When I drove it, it shifted smoothly from 1st to 2nd, and 2nd to 3rd. But it will not shift up from 3rd. It shifts back down perfectly fine. What could be the problem?