Ford-O-Matic slipping when warmed up

Hello all. This is my first post, and my first car project. I just finished taking the engine, transmission and rear end out of one '59 Edsel Corsair and putting it into another. I also lowered it 2 inches with the help of another thread here. It worked perfectly and glad you are all here.

Now, getting to the point... What is happening is that when I start the car, the transmission works properly. Reverse works. First works, and it seems like it goes into second. But, I have not had the car going faster than about 25mph, so I understand I may be wrong about that.

As soon as the car warms up, I lose pressure in the transmission, and the car slips out of gear for about 20 seconds, or more. Then it comes back in slowly. I can drive for a bit longer, and the whole thing happens again.

I haven't pulled the pan and cleaned the filter yet, so I am going to start with that. But, if anyone has some insight, please feel free to share.

I knew the ****** was questionable when I put it in, but it was better than the other.

Thanks

 

Vacuum modulator? Plugged filter? Is this a 2 speed or fmx 3 speed?

 

2 speed. Hoping a plugged filter. Will find that out as soon as my gasket comes in.

Mainly trying to see if other people had the same problem before.

 

may not have a filter. drop pan and clean strainer or screen ,, also is the fluid full check dip stick at idle when engine/trans is at operating temp.. NOW ADD some intro type info.

 

I guess I shouldn't have used the word filter. Was expecting it to be a screen. Checked it at operating temp and it is full. The gasket will be coming in next week.
And, I thought I already added intro info. Will get that out soon.
Thanks.