Forgive me if this an obvious question, I'm new to this. What is the model rearend used in 2001 1/2 tons? I have a 1500 Sierra that has an open rear that i would like to upgrade.

 

There are several options, if you are able to look in your glovebox and find the list of three digit codes, look for the one of the following codes

GU2 2:73 ratio

GU4 3:08 ratio

GU5 3:23 ratio

GU6 3:42 ratio

GT4 3:73 ratio

GT5 4:10 ratio

GQ1 Open Differential Rear Axle

G80 GOV-LOC Rear Axle

Hopefully I understood your question correctly?

 

That actually cleared up my next question, thanks for the info. But my original question concerned what model (dana 60, GM 12 bolt, Ford 9", etc.) the rear axle is so I order the right parts for it. Thanks!