I have a 2006 aveo.before it would go 25 mph.I put granny fluid in it ,it would pick up speed .now it's leaking and it will not even do that.someone said it's a closed system and cuzz it's leaking ,that why it won't hardly move .is that true or is it something else?
If you are low on transmission fluid , you will not be able to effectively transfer power through the torque converter.
Not to mention the lack of lubrication/cooling as well as fluid pressure to activate your clutch plate.
Find the leak, repair it and top it off to the proper level and hope there hasn't been any damage.