My friends 700r4 jerks really hard when shifted from park to any gear.. other then that it shifts competely normally in every other gear.. what are possible causes?

To high of an idle, the U-Joints are bad, or the tranny mount.

1982-1986 units did not have a forward accumulator, that is why they tend to hit hard from park/neutral to any forward position. Starting in 1987 they used a forward accumulator which softened the engagement.

Probuilt,
Is this accumilator good or bad or indifferent doesnt the soft engagement put additional wear on the clutch packs

The earlier units that ddid not have an accumulator were very hard on the front clutch splines. The later units with an accumulator have very little wear at the splines and very little wear in general. Remember that you only engage this accumulator when you go into a forward gear, and it does not disengage until you take it out of the forward pattern.