Got my 700r4 together last week and got a press gauge on it today. Here's the numbers.

As you can see the press is low across the board.
Fluid level is full. Filter is new. Tranny was warm.

Original governer for 87 GTA as far as I know.

It will not stay in OD at any speed or throttle setting.

It's a little reluctant to shift into 3rd.
On stands, it shifts into 3rd at 55mph and 2300 rpms with 65 psi.

If I power-brake in rev, press is 95 psi.
If I power-brake in OD press is 65-70.
If I power-brake in 1st or 2nd, press is 80 psi.

All press readings taken at the press port just above the shift shaft.

I'm hoping it's not the pump, but what else would give me such low readings?

 

Found the problem. One of the TV boost springs somehow got installed on top of the PR valve. This was keeping the PR valve from closing. Got the springs in the right places and the pressures all jumped up into spec. Tranny shifts thru all gears normally.

 

Hey when you have been at it as long as I have you realize stuff happens glad you found it