Coolant running down transmission

While running hoses for a trans cooler on my '21 with 51k miles, I noticed dried coolant around the "warmer puck" area of the trans. Could this be a valley plate leak, or leak from somewhere else? Debating whether to install the trans thermostat or not before I take it in for diagnosis.

I did not see any signs of coolant leaking from up top or higher on the lines going to the warmer puck.

 

Could just be the o rings on the puck itself. If it is your install should fix it and if not, I doubt installing a thermostat would impact the diagnosis at all.

 

If o rings leak they leak atf fluid not coolant.

 

Check it from top of the engine. May need inspection mirror.

 

Fair point lol

 

To me that looks like a valley plate leak. Pretty common on these 5.7s and a fairly involved job to fix.

 

Couldn't find any pink stuff from the top. I'm taking it in to have it looked at. Appreciate all the feedback!