* TH350 (Turbo-Hydramatic 350): This was a very common three-speed automatic transmission. It was likely the most prevalent option.
* TH400 (Turbo-Hydramatic 400): While less common than the TH350, the TH400 was a heavier-duty three-speed automatic. It was more often found in trucks with larger engines or those intended for heavier towing.
To know for certain which transmission was in *a specific* 1984 Silverado, you'd need to check the vehicle's documentation (owner's manual, build sheet if available) or look at the transmission identification tag located on the transmission itself.
