Transmission gurus-where are you?

[chilcutt]

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?