* 4L60E: A four-speed automatic transmission. This was by far the most prevalent option.
* 4L80E: A four-speed automatic transmission, typically found in models with larger engines or heavier towing packages.
To know for sure which transmission was in *a specific* 1999 Chevy Suburban, you'd need to check the vehicle's documentation (like the owner's manual or the sticker on the driver's side doorjamb) or look at the transmission itself (though this requires some mechanical knowledge).