* TH700R4: A 4-speed automatic was very common.
* 4L60E: Another 4-speed automatic, becoming more prevalent in later 1993 models.
* SM465: A 4-speed manual transmission was also available.
To know for certain which transmission is in *your* specific 1993 Chevy Silverado 4x4 V8, you'll need to check:
* The VIN plate: Sometimes the transmission is coded on the VIN plate or a sticker on the door jamb.
* The build sheet (if available): This would definitively state the transmission.
* The transmission itself: Look for markings on the transmission case. This requires getting underneath the truck, and some knowledge of what to look for.
Without more specifics about your truck, it's impossible to say with certainty which transmission it has.