My M46 OD is having trouble. I can no longer get the car
into reverse. It also does not downshift, when placed in
a lower gear, the RPM drops to idle without any engine
braking.

I talked to Duane Hoberg and he recommended replacing
OD unit. I have obtained a new transmission from a 1982
donor car, and almost finished installing it.

Now comes the problem. I did not think to check on the
size of the output flange. My car has the larger size
driveshaft, and the donor car has the smaller size.

For the OD image see the link below:
http://www.brickboard.com/FAQ/700-900/OverdriveExplodedDiagram1.htm

How do I remove the output flange (61) from the rear of the
transmission? There is a nut (64) that looks like it is
holding it in place. I have the new transmission in the
car, and turning the nut rotates the engine against its own
compression. I also need to remove the flange from the
old transmission that is off the car. I am stuck on this one.