So I noticed something. The suburban I bought has the traction control button. And it has a traction control symbol on the dash as well. But I have no rpo code of nw7 in the list. Can someone clarify this for me?

 

TC button is part of the ABS system.

 

You do have a limited slip differential - that is what the G80 RPO code is for. What that means is that if there is a measurable difference in the speed of one rear axle than the other, the rear differential will lock up. I think it is purely a mechanical function of the differential. Technically it is the "Eaton" locking differential, in use since the 70's by GM. Here's an article I found on it:

https://www.autoevolution.com/news/a...ial-94874.html

The button on the dash is for Stabilitrak, which uses the ABS system to help maintain traction, by applying the brakes independently per wheel while moving, if a speed difference is seen between wheels. You press the button to turn it OFF (a light comes on to indicate it is disabled). Stabilitrak is useful to prevent things like hydroplaning, but relies on the vehicle to be moving (all 4 wheels rolling) before it does anything. It won't help when you are stuck. I thought it would myself one time, when my Yukon 2WD was stuck in the snow, but I had to get out and put chains on to make it the last 50 feet up a hill to a cabin I had rented in NC...