To find it precisely, you'll need:
* Your Riviera's year and model: This will help narrow down the specific transmission type and its location.
* A repair manual specific to your car's year and model: This will provide diagrams and detailed instructions. A Haynes or Chilton manual, or a factory service manual, are good options.
* Possibly a flashlight: It can be tucked away in a tight spot.
Without knowing the specific year and model of your Buick Riviera, a more precise location cannot be given. Consult your repair manual for the most accurate information.