I need to replace the assembly that mounts underneath the vehicle to hold the spare tire. There is a cable, with a "T" at the end, in a housing that allows you to crank the spare up under the vehicle. What is this called?

 

i would call it spare tire winch

 

I tried "winch" under the parts websites and only get things like Warn bumper winches. Any idea what GM calls it? Or a PN?

 

i don't know what they call it but everybody on ebay list them as spare tire winch that is where i would go to buy one

 

Go by your gm parts counter and have then show you one of those exploded diagrams.

 

Try searching on "spare tire wheel hoist"