When the car is hot after being driven for a little bit - coming from a stop acts like it is in neutral

I have had the radiator replaced because my trans fluid was grey and watery. Also I have had all the gaskets and o rings and thermostat replaced and the car still smells like coolant after being driven for a little while. Before the Tran fluid/system was flushed and fluid replaced, the car would not go after being stopped. It feels like it is in neutral.