'94 Plymouth Alliance 3.0. Had a broken engine mount; the current mystery
noise was heard among the other sounds made by the broken mount, and the
mystery noise was assumed to be caused by the mount. Transaxle was
rebuilt (the place is known competent) and mount replaced, but the
mystery noise persists.

There isn't anything I can identify the noise with. It's from the front
right side of the car, sounds like thick metal parts hitting each other.

Pull down the driveway. Go over the flattened curb section - BONK
Turn left - BONK
100 feet to intersection - nothing
Turn right - BONK
Down street, hit bump - nothing
Veer slightly right - BONK
Straighten out - nothing
Veer slightly left - BONK
Straighten out - nothing
Stop - nothing
Turn right - BONK
Steer slightly right and left - nothing
Turn left - nothing

Now that it's been driven for a minute or two, it will make the noise
less and less in response to slight steering. Normal steering is the
most likely thing to get the noise, but not consistently. There is no
change whatsoever in steering, road feel, braking, or anything else
between noises. Braking of any sort does not seem to cause or prevent
the noise.

Accelerate or decelerate during turn - nothing
Hit bump - 10% of the time BONK, 90% nothing
Hit bump immediately after steering - likely BONK
Jackrabbit acceleration - nothing
Panic stop - nothing
Parked, bounce car up and down - nothing
Wobble tire & wheel - no looseness or play
New brake pads & rotors - no difference

I haven't found anything I can do to make the noise five times out of
ten, nor anything I can avoid doing to prevent the noise five times out
of ten. That's why it's so mysterious. Ideas appreciated.