Ever since I got the car it has shifted pretty hard, but I learned to live with it. But crawling in traffic or going slow when it shifts gives a very noticable jerk and an associated snap/clunk sound which I assume is play in the driveline.

Anyway, tonight I went under and turned the trans modulator 2 full turns BACK, and this seemed to have very little effect.

In the morning, when the engine is cold, it will shift nicely, not too hard, not too soft. I think this is from a cold-start vacuum valve that allows it to shift softer when it is cold, because these normally shift hard when they are cold, but it only does this for about two minutes.

Did I turn it back far enough? Maybe I have a leak in the line to the vacuum modulator?

Any suggestions?