Automatic transmission is shifting hard.

Was the engine replaced with a direct fit engine? Were any sensors or computers changed? Is the transmission the original one?

It sounds like a bad shift solenoid, but I'm trying to determine what would have caused the problem since the engine replacement. Have you checked for vacuum leaks? Have you checked wiring harnesses to the trans control module, grounds, and wiring to the PCM?

Check around the transmission for the trans control module. You will see it. It could be something as easy as running a seperate ground from the transmission to a good solid ground on the body of the vehicle. Sorry I had so many questions, but when the engine was out, it is very easy to over look things or miss something small. I just trying to eliminate things. The wiring should be easy for you to see and check. Make sure the harness plug is tight and clean. Make sure none of the wires were scraped and allowing them to short. For the heck of it, try running a seperate ground to the body to see if that helps. The problem sounds like a shift solenoid issue, but what caused it is the question. They don't go bad because a new engine was installed.