GTZ shudder at hwy speeds

[alphapygmy]

Hi all, my wife's 2003 GTZ has been acting up the last 6 months, though very infrequently. It has 180K miles and has had oil and trans fluid changes at the suggested times. She will be slightly accelerating or steady at 50-60mph and the car will give a jerk or two then be fine for another month. Seems to do it more when it's hot out. My thought was the torque convertor is shuddering. I tried half a bottle of Lubeguard red and it seemed to help for a little bit. The car shuddered several times last summer but hasn't again until today. She also said she was in a hurry and switched from Reverse to Drive while the car was still rolling backwards. Torque convertor? Solenoids? Plugs looked good and are not fouling. Murphy's law we just spent a ton of money buying me a new rig and 2 days later her car starts acting up. Any ideas? Thanks

[greddy]

torque converter is a likely suspect, doubt its the solenoids. V6 auto trannys aren't known to take abuse well.

[alphapygmy]

Torque convertor is what I figured. It's had regular fluid changes and it's almost due for another so I'll just do it early and add a bottle of Lubeguard red. On another thread someone mentioned Valvoline Maxlife synthetic ATF has very good anti-shudder properties so I think we're going to try it. Really would like to get another 18 months out of the car but we'll see.