I'm sooo excited

Please please help Engine/Trans problem

Just got the car running today and did the break in. After i broke it in i decided to take a test drive. When i went to put it in gear it didn't move. I checked the tranny fluid(C4). It was a little low. Added fluid, then when i put in reverse it wanted to lunge forward. And take off. I also noticed that when i added the tranny fluid the car acted like it fell on its face and completely lost power. It became less responsive and sounded like it was bogging down. Before i put it in gear i could turn 6000 rpm easy. After i tried putting it in gear it struggled to reach 3000-3500 rpm. When it started doing that the engine started surging as well.


Here is the kicker, Shifting from park to reverse it goes forward. Same with nuetral. Every gear is "Drive", except Park.

What exactly does the vacuum modulator do,?, and how bad will it affect the car if it is not working properly?
Also do i have to have the kickdown tube hooked up just for a test drive.?.
I have done research on the site, and there is one thread that was similiar to my problem but his was fuel related.

Any kind of help would be greatly appreciated.

I didn't mess with the tranny at all.

When i re-installed the motor, i did have to suck the motor to the trans barely. Only like an 1/8 of an inch. If that be the case is it costly to get fixed.

Also how come it didn't start acting like that till i put it in gear.

What would be your suggestions to fix it.