What causes shudder at torque converter lockup

GOOD tune up should do the trick!

New plugs & wires. it has slight hickup idling in gear at stop light and car tries to move with miss at times but goes smooth when put in neutral

When the car gets into the highest gear (converter locked) ANY engine misfire is amplfied and just might feel like a shudder. Probably not felt in any lower gear. Scanner needed!!