To find the exact towing capacity for *your* specific 2008 Silverado 2500HD, you should:
* Check the sticker: Look for the sticker on the driver's side doorjamb or the glove compartment. This sticker will list the maximum towing capacity for your truck.
* Consult the owner's manual: Your owner's manual will have a section detailing towing capacities based on different configurations.
Without knowing the precise configuration of your truck, I cannot give you a definitive answer. However, expect the towing capacity to be in the range of 8,000 to 10,000 lbs, but it could be slightly higher or lower depending on the options.