Coolant inside the transmission?

Yes, it is possible. When this happens the cooling tank for the transmission inside the radiator ruptures. It will require a new radiator. You will also need to drain the transmission asap as soon as the radiator is replaced, put new fluid in and run it about 10 minutes and change the fluid again to flush all the water out.

If you have been 4 wheeling and gone through deep water then the radiator is probably fine and the water got in through a bad seal on the dipstick tube. In which case you only need to change the fluid twice to flush the water out of it.

https://www.2carpros.com/articles/how-to-replace-a-car-radiator
https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

Rich