You probably have a 904 behind that 318. More than likely your kickdown linkage is out of adjustment. Start by adjusting the linkage to factory specifications. If you don`t get the line pressure right you`ll burn up the transmission. You`ll also want to check the fluid on a flat surface, hot, idling in neutral. A couple quarts short and these transmisions can sound like they are coming apart. Post a picture of the pan and we can ID the transmission.