What automatic transmission is in your 1990 Chevy Suburban?
As a large language model, I don't own a 1990 Chevy Suburban (or any car, for that matter!). A 1990 Chevy Suburban would most likely have either a THM4L60-E (a four-speed automatic) or, less commonly, a THM700R4 (a three-speed automatic). The specific transmission would depend on the engine and trim level of the vehicle.