This evening I swapped-out the rear differential speed sensor ($95 from the dealer -- only 1 dealer had it in stock in all of my area.)

- Start the car.
- Put in drive. This time, there was no hard JERK.
- It shifted smoothly through all the gears.
- The ABS light went out as soon as it hit 2nd gear.
- The check engine light stayed on for about 10 miles.