How Often should I replace my transmission fluid? It's a Brougham, not a Fleet on 1991 Cadillac Fleetwood

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
My car is a 1991 Cadilac Brougham. The system won't include this model in the list of choices.
(1) Answer
| |
approx every 30k to 40k miles
Qualified Local Cadillac Shops
Qualified Cadillac Shops For This Repair