Yesterday I was driving up a moderately steep incline, car was cold having just left home, and someone backed out of their driveway right in front of me.
Well I braked and had to pull up rapidly, not screaming to a halt but just rapidly, and there was this nasty metallic *clunk* as the car droppd into 1st from wherever it had been.
I'm going to try and replicate it later today in a more controlled manner to try and detect where it comes from.

The auto has been well behaved, but occassionally I do experience these annoying shocks downshifting to 1st, wish I knew whats causing them and where they're happening.
Maybe related to the shock I get when shifting into reverse when cold. I've been "pre-shifting" by moving into reverse and quickly out again before the thump happens and then back in. This seems to avoid the shock. Its not too bad, but it is irritating.
Meanwhile my old KH continues to shift smoothly and quietly after 240,000 k's ...

front engine mount?

front engine mount?

Check this, also diff for excessive backlash, driveshaft joints.

Could be electrical - TPS setting. The second gens used to do what you describe if the TPS was off.

Could it be that the car's engine, being really cold, was just revving hard and the clunk was just a reaction to the rapid downchange?

Couldn't replicate it.
Engine mounts were replaced a little while ago.
Even if the car is cold, it should be smooth.
Yeah, I do have this backlash which thought was the diff.
Dk about the driveshaft joints. How to check those?

Check for something loose in the boot?

Um, my bad, turned out to be something loose in the boot.