What causes shudder at torque converter lockup on 1994 Cadillac Fleetwood

about 45 to 50 miles per hour

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2 answers 4 comments
Torque converter itself or engine misfire(s) that's more pronounced with converter locked. Light on?
No CEL after fully warm 30 min any heavy gas pedal and its there add on occasional not
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!!
If it's only when 'lock-up' occurs , try doing a trans fluid chang, using factory fluid. (NOT a flush) see if that helps the symptom.