about to put on some OEM tranny/coolant fluid back into my car, but does anyone know if i should drain it out?? or should i just fill it back up to the top?

both can be done correct?

 

if want a better quality job you need to drain the fluids so you wont need to do it again for awhile its the same thing like if youre leaking oil you cant just keep adding quarts and not change the filter there is trash in there that needs to be drained