rough shifting '02 L100 w/ 41,000 mi

I am into month 3 of an intermittent shifting problem. 98% of the time
shifting is smooth, the problem arises usually when the car is warmed
up. Symptoms of the poor shifting will be a delay past the usual rpm
point of shifting with a "slamming type kick in the pants" changing of
gears.
The dealer has changed the input speed sensor and the pressure control
solenoid twice. The difficult aspect of all this is I spend days
waiting for the problem to duplicate for the mechanic (he drives my
car) where he will then attempt a fix. The last time I was told they
will call Tech Support for help. They phoned me yesterday to tell me
they were still driving/waiting for the problem to duplicate again, my
thought was why? Well, the mechanic is obviously stumped.
I Googled and found this:
http://groups.google.com/groups?hl=e...%3D10%26sa%3DN

Does anyone have any suggestions? My patience is wearing thin.