I replaced the crappy oem plastic shifter (the button jiggled around) with an aluminum one that looks identical. When I installed it, I had it in 1st gear so I could easily get to the bolt. While in 1st, I unscrewed and removed the original and then tightened down the new one. It shifted back to park fine. When testing it (going back and forth from park to 1st) one time it was hard to shift and took pressure, I heard a weird noise, then it moved past. Did I possibly screw something up? I tested it about 10 more times and it's shifting fine, so I'm not sure what happened. After I had already installed it I noticed on the bottom of the box there were folded instructions that said to only swap them when it's in park. I've taken my shifter on and off many times previously when it wasn't in park and didn't have an issue. What could that noise have been and why did it take pressure one time to shift? Thanks!

 

That is probably a safety warning to only remove it in park. They don't want some idiot to remove it in neutral and roll down the driveway and drive over the neighbors kid.

 

I have always removed my shifter down in the first gear position to access the allen screw easier. That wouldn't cause any issues. I would try to back out the screw maybe half a turn. That screw is not meant to be tight but to just hold the shifter arm on.