As I go through the works on my 2001 430, I am trying to get a hold on how "things should feel" and sound.

I understand It's hard to have this over the internet but I do not have another 430 in pristine condition near me to set that baseline.

To my question for this thread:

Going from P to D or P to R: a single thud when the gear engages that you can hear just enough but that can be felt.

I replaced the engine and transmission mounts recently. This "issue" was present before, hence the replacement of the mounts.
I also did a drain and fill (fluid previously stained napkin dark brown with traces of black)
The mechanic made a mistake the first time when he did the D+F and added too much.
As a correction, at the same shop but with a more knowledgeable mechanic, he drained some fluid out, we got to be under the "hot mark" while the engine was running and warm.
Added some 200-300ml back in and we are now at the top end (just barely touching the last notch on the hot area)
All in all, we used 4.5L in between the first D+F and the corrective drain to fill to a correct level.
ATF is now staining deep red with some black still.
No burnt smell that I can detect thus far.
We are planning a pan drop and filter replacement.
Gear changes fine with no noticeable feel during the gear changes when driving.
I am a slow-ish driver and I prefer to drive relaxed.
Highway driving is solid.
No flares.
No hesitation when doing gear changes.
Also, we replaced the rear diff oil.

As it has not gone, I wonder what else it could be or...whether it is normal to feel the gear engage.

If I am testing this clunk/thud, stationary, going from R to D generates a harder clunk.
Going from R to N to D slower reduces the clunk-y-ness.

Have not found a video online that would show my issue best. I've seen a few that are a lot more extreme than mine with other vehicles.

Open to all wisdom!

 

Check U-joints

 

Just checked my 2001 and no problem. As mentioned check U-Joints. Also president of Aisin plant in NC told me years ago that most of transmission problems happen with underfill, overfill, and contaminants.