Hard downshift from 2nd gear to first. A-833 4-speed.

in your first post you mentioned that you put in a dual diaphragm clutch in the car.
Did you mean a dual disk diaphragm clutch?
If so check the departure on the second clutch disk(closes to the trans). On sum of these dual disk clutches the disk will hang on the input shaft and keep spinning with the pressure ring. The cure for this, is to set the clutch up with a little more departure and to grease the input shaft with a special grease thats helps to keep the disks sliding on the input shaft.
The new Challengers with the 6 spd. all seem to have this same problem.