What automatic transmission is used in a 1990 GMC Vandura 3500?
The 1990 GMC Vandura 3500 typically used a TH400 3-speed automatic transmission. However, there's a small chance it could have a different transmission depending on the specific options and engine it was equipped with, but the TH400 was the most common. To be absolutely certain, you'd need to check the vehicle's identification number (VIN) and consult a parts catalog or a GMC service manual for that year and model.