Thanks for the input, everyone.
My thinking (perhaps overly wishful) on the TPS was that the transmission is not getting a proper signal to "go" at operating temp 'til I bump the revs.
I tried cleaning the TPS on my other SVX to no effect. Ultimately, replacing that one cured a gear-hunting, weird-inappropriate-AWD-bias condition.
Have not shifted from "D" to "3," nor tested in FWD. Will do.
It's not just in drive, also reverse. I first really became aware of this when backing into a parking space on a nose-down incline. At idle, if I don't hold the brake the car will roll forward—selector in "R"—as if in neutral. Waiting for a car to pass before making a left recently, incline reversed, in "D," the car wanted to roll backward.
At or above, say, 1000 RPM, all seems good. I drive this car 2-3 times per week at minimum (25+/- mile RT, 2-lane, curvy, rolling terrain) and have noticed no other worrisome behavior.
Transmission was alleged to have been recently rebuilt when I bought the car @104,000 miles. My "proof" of this: An e-mail from the salesman.
dcb