My heatercore started leaking and caused me to.

My heatercore started leaking and caused me to overheat, bypassed system, then my thermostat went out causing overheating again.
while I was fixing the thermostat, (heater will have to wait) I changed the oil and filter, and the plugs and wires.

now the transmission doesnt down shift at all. I turned the car off and started it again and it goes straight to the rev limit.

please help if you can thanx