904 tranny problems

Is the kickdown linkage hooked up and set correctly? It will cause the exact issue you are having, if it ain't right.

No No No. Improperly adjusted throttle pressure linkage will not cause a car to not move at all. You could take it completely off and the car would still drive forward and backwards, it'd burn up the trans. with it removed or maladjusted but it'd take off.