Toyota Mark II: Automatic Transmission Torque Converter Lock-Up Shudder

The A340E automatic transmission fitted to both JZX90 and JZX100 Mark II variants uses a lock-up torque converter that engages at 60–90 km/h under light throttle. After high mileage or extended periods without ATF changes, the clutch friction material inside the torque converter glazes and causes a pronounced vibration or shudder as the converter attempts to lock. The symptom is closely tied to fluid condition — partially degraded ATF loses the friction modifiers required for smooth lock-up engagement. Toyota issued technical service bulletin guidance on this issue for the A340-series transmission.

• Rhythmic vibration or shudder felt through the seat and floor at 60–90 km/h under light throttle — sometimes described as driving over a cattle stop
• Shudder disappears when accelerating firmly or coasting — only present at the lock-up engagement point
• ATF found dark brown or black with a burnt smell on dipstick inspection
• Hesitation or rough engagement when the transmission upshifts into overdrive at highway speed

Test drive the vehicle on an open road at steady speeds between 60–90 km/h with very light throttle applied — replicate cruise conditions. A shudder or rapid vibration through the floor and seat at this speed range under light load that disappears when pressing the accelerator further or lifting off completely indicates converter shudder. Pull the ATF dipstick with the engine warm and transmission in Park — ATF should be translucent red with no burnt smell. Dark brown or black fluid with a burnt odour confirms degraded fluid as a contributor.

Parts involved: Torque converter.

$350 to $3,200 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Does the car shudder or vibrate at around 80 km/h when driving at a steady pace?”
• “When was the transmission fluid last changed, and what fluid type was used?”
• “Has the transmission ever been serviced with a flush or has it only had drain-and-fills?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.