Antifreeze in transmission 2010 Duramax??

[ivbinconned]

What’s going on here. How does this happen? And has it ruined my transmission?

[Grit_dog]

^What he said.
And also a real kick in the nuts, as this is not a common issue. And not one to be expected nor prepare for. Especially in a vehicle that new ( unless it has a pile of miles on it maybe).

[opnspaces]

You have a leak in the transmission cooler that is inside your radiator. And yes it's very possible it has ruined the clutches in your transmission. You definitely need to get the radiator replaced and the transmission flushed multiple times. Then cross your fingers and hope that the transmission survived.
bottom line get the radiator fixed right now.