Hi Scotty I have a 2018 Colorado ZR2 V6 gasser that comes with an eight speed transmission with 25K Miles on it. Is the eight speed transmission the same transmission they using in the Silverado's that they're having so many problems with mine shifts smooth as butter right now. Also in some of the chat rooms I've heard people talk about the differential vent lines I've never heard of this, what's the what is the purpose of venting the differential and if I go through deep water will water get into my differential and is that something I should be monitoring.
To address your first question, you have the 8-speed Hydra-Matic 8L45 same as the Silverado and many other GM products. I am not a fan of that transmission and consider it one of the worst GM has made recently. I consider it a deal breaker for any GM product. There was even a class-action lawsuit against it:
https://www.carcomplaints.com/news/2019/gm-hydra-matic-transmission-lawsuit.shtml
GM’s triple flush seems to address the issue (supposedly), but jury is out on the long term health of those transmissions (with that supposed fix):
https://gmauthority.com/blog/2019/08/tsb-seems-to-fix-8-speed-automatic-gm-transmission-problems/
The differential has a breather valve on the top of it so there isn't a vacuum inside the case. You can get a fitting that threads into the breather hole and run some tubing up to your tail light bucket. No more worries about water in your differential.
