In the morning when first warming up my car if I put the car in drive too early it will just go into reverse occasionally. Once the car is warmed up no problems. Any thoughts on whats causing this?

Oh its a 289, 2v, c4, all stock.

 

Check your fluid level. When was the last time you changed the fluid?

 

There might be a problem with the torque converter draining back into the trans case overnight. I believe there is a checkball in the pump that controlls this.

FWIW.

 

I am not sure the last time a fluid change was done. ( I have only had the car a few months). I will get new fluid and a filter though and change it. Any recommendations on type?

I was thinking torque converter too. The transmission was rebuilt in 03' (found a receipt in the glove box).

 

A few years ago I had an old Ford truck with a C-6 auto. When cold it would only go into Reverse, but after it warmed up a little while it would shift fine like it should.
I changed the tranny filter & fluid and the problem went away.

 

You should use F-Type ATF or something compatible if it is a 3 speed C4 or C6. AOD or EAOD will require something in the Mercron/Dextron rating.