1999 Grand Caravan 3.8 intermittent shuttering when shifts

Where would I start to troubleshoot some intermittent shuttering when vehicle shifts through the gears.

This does not happen all the time. if it does, it seams to happen when traveling at highway speeds and when you step on it to either pass someone or just to speed up.

I have a scanner and no Codes are in history or current.

Gary

Sounds like a TCC (torque converter clutch) problem. I would try servicing the trans (flush the fluid and change the filter).