700R4 no pressure when cold
 

I have a 1984 diesel van with the 700r4 transmission. This rig suddenly started not moving when cold. No gear did anything till it was allowed to warm up. I put a gauge on it and it literally has zero pressure when running cold. After 15 minutes or so when it starts warming up the transmission will gradually start showing an increase in pressure. At about 30 lbs you can move it and I believe all gears will work. If allowed to get hot you might see as high as 60psi. needle on the gauge jumps around a lot. I pulled the pan off but could find nothing obviously amiss. I figured maybe the pressure regulating spring had broken but it seems fine.
Thoughts?

Re: 700R4 no pressure when cold
 

30 PSI is low. It sounds like something in the Pressure regulation system failed. You're on the right track.
Besides the pressure regulator valve there's a spring loaded relief valve and the TV cable valving. Is the TV cable working?

Re: 700R4 no pressure when cold
 

TV cable is working fine. The part that's throwing me is the no pressure cold part. Usually if a transmission gets worn it will have pressure cold but not hot. The gauge needle jumping like it does seems like another clue I'm missing. I suppose there is nothing for it but to pull the transmission and take it apart on the bench. ugh. Not looking forward to that.
Oh and another thing TV cable position does not seem to have any affect on pressure. I mean even in Neutral I should have some pressure right?

Re: 700R4 no pressure when cold
 

Pump rotor vane seal maybe? Had plenty of autos that slip and won't engage when cold. Warm em up and the lip seals start holding pressure.. Usually only effects one clutch pack, maybe 2. I would look more at the pump considering you have zero pressure. If your gonna pull it apart, might as well overhaul it.

Re: 700R4 no pressure when cold
 

Yep I think that's what I'm going to have to do. Thanks for the advice.