Transmission gurus-where are you?
 

From the day I got my 79 300 SD, the transmission has been finnicky. What it does is- when the car is first started and put into gear,sometimes she goes and sometimes she dont. When it does not move, if I put it in park and accelerate to 2,000 rpm for about 1 min. the car drives. Same thing after it has been driven and parked(say to go in a store) , sometimes she goes and sometimes she dont, until accelerated for 1 min. Have fresh fluid at the corrct level, and new filter, so that is not the issue. What are possibilitys, hopefully this is something I can repair myself. Ideas?

My recollection is that this symptom is indicative of worn seals. The fluid has to warm up a bit for the seals to function. I've owned a couple of Dodge vans that behaved this way. It typically happened when the vehicle sat for extended periods.
It may be one of those cases where a 'Fix-in-a-can' may be helpful in rejuvenating the seals.
On the other hand, it could be a sticky B-2 piston I think.

I have suspected the B-2 from day 1 and will check into that. The car did sit for awhile before I got it, just wondering if there is a specific fix-in-a can that should be used as to not hurt anything inside. Maybe I will try that first.