To previous comment, you are right about everybody has done it once or twice, but it is a fact that over time, changing gears in an automatic while moving, doesn't matter if you're barely moving or not, will eat at the gears to where you notice it shifts slightly harder.
And changing gears while moving can break the engine mount; doesn't matter how slow or fast you're going.
Come to a complete stop before changing gears.
If your transmission is shifting harder only when going from park to reverse or drive, that most likely is a broken engine mount.
And another thing that can cause hard shift is bad, dirty, burnt, aged and contaminated transmission fluid. By reading your mileage, it looks like you're due for a transmission flush anyways.
"And changing gears while moving can break the engine mount; doesn't matter how slow or fast you're going."
Yes, this is true, however it reminded me of a demonstration I saw some years ago of the ruggedness of GM transmissions. A new Oldsmobile was repeatedly shifted between reverse and drive while the accelerator was held on the floor. This was done for 15 minutes and generated huge clouds of tire smoke. After the test, the car drove perfectly. These transmissions can take a lot of abuse.
I had a friend who had the brakes go out on his old '78 Monte Carlo. He drove it for two weeks by stopping it with the transmission by jamming it in park. It didn't hurt it at all.
To previous comment. I agree with you completely. These GM transmissions will take a beating. Pretty much like all GM products. I'm a GM guy all the way.
I was just stating things that can cause hard shift. In no way was I talking bad about build quality of any GM products. In my opinion, GM is the best vehicle manufacturing company and I thought I would make it clear I wasn't talking down on GM products. Just stating thing that can cause hard shift.
Seriously man, change the transmission fluid. I had a Saturn do something similar, and after I had it changed, it stopped.