First shift in the morning.

My '96 Estate Wagon shifts really hard going into gear with the first shift in the morning after a cold start. It doesn't matter if I engage "D" or "R", there is a short pause, then it slams into engagement. After the first shift of the day, everything is normal. I kinda suspect that the torque converter is leaking down and then refilling with a bang. When checked hot, the fluid level is normal. Maybe I should check the fluid when the car is dead cold, If it's really high that could be a clue. Any suggestions as to the cause, and better yet, a cure.
Jim

A torque converter drainback valve failure feels like a soft engagement, not a harsh one. As the torque converter refills, it feels like a third gear start, and then everything gradually returns to normal over about 10 seconds.

I would check the forward accumulator and the forward abuse valve, which may be somehow getting stuck open and then it releases once things get going. I just recently drove a 4L60E with a very harsh forward and reverse engagement and my guess is the forward and reverse abuse valves were stuck open. The trans was filthy inside, so step number one was cleaning out the pan and then flushing the fluid.

Have you flushed the fluid and cleaned out the pan in the trans?

No I haven't, but sometime next week It'll happen.

perhaps its just idling high when its cold,