Transmission shudder

[geno4952]

My 2002 GP GT has a slight "shudder" when shifting from 1st to 2nd gear (auto trans), it only happens when everything is up to temp and only at higher (3700 or so ) rpms. Anyone have any ideas what this may be. It has done this since I bought the car. It had 63,000 on it and now has 73,000. It is no worse now than it was then. Thanks in advance for any help.

[Jakescoots]

maybe a tranny solenoid