2004 Chevy Silverado 2500HD

Hello, This may be a stupid question to some, I bought this truck about a month ago. 2004 Chevy Silverado 2500HD with the heavy duty trailoring package and snow plow prep package with 4.10 axle ratio and locking rear dif. This will be my tow vehicle for pulling my camper. It also says it has a Heavy duty 4 speed transmission. wich looks like was a 1,200 dollar option. What makes the transmission Heavy duty?


thanks everyone.
Eddie