I am looking at buying a 2005 Chevrolet Silverado 2500HD Work Truck, 4dr Extended Cab Work Truck 4WD SB, VIN# 1GCHK29U85E280923
it does not have a factory hitch installed. does this tell me that the frame? axle? trans? or ? anything will be less capable of towing than a truck that came with a factory hitch ?

 

No. What that tells you is that it may be at the bottom end of the towing rating for a 2500HD of that year. I would look at your owners manual. If you don't have it, here is an online copy:

https://assets.gm.com/manuals/chevro...ado_owners.pdf

Towing a trailer starts on page 4-69

Decoding your VIN (use the tool above) tells me you can tow at least 10,000 pounds with a weight distributing hitch. You can get 12000 if you are properly equipped (extra oil coolers, right differential, etc). The manual seems to indicate that 10,000 pound limit as well for a K2500 with extended cab and short bed.

I have a 2006 Silverado 1500 work truck, and the prior owner put a U-haul receiver hitch on it. However, the vehicle is already wired for trailer lights and all that. There is a panel above the drivers side axle, facing rear, that has places to plug in the the tail lights, trailer pigtail, and other things at the back of the vehicle.

 

Check with a local hitch shop on the cost of the receiver assembly and labor to install it. Or go to etrailer.com and check their prices for a DIY hitch install.