[donk.]

Ugly situation for both parties...

Dealership may have gotten a lemon and not even know it, often time trade ins are driven around the block and that's it.

Hopefully they find what destroyed the transmission, often times something else knocks it out, and get all issues fixed

IF you have warranty, you have warranty. Walk into the store like a man, ask for the manager, tell him what's up without making a scene. Tell him you need a car asap (loaner, or other car, payout, etc), hopefully come to an agreement. If he goes into sleazebag dealership mode, then you start making a fuss infront of all the other customers, and leave them honest reviews online

I had the same situation, bought a truck with the dealerships "certified" form, took it to my mechanic a week later for an oil change, and he straight up told me to return the car because it was so bad.
So I did, I walked in, told them to take their car back, owner of dealership told me he would fix all the major issues, and it worked out for the both of us. Huge time waste on both ends, but that's unfortunately the price you pay buying used.

Can't comment on legal action / VSA etc, i hope everything works out