Lexus IS: A960E Torque Converter Cold Shudder (IS250)

A widely documented IS250-specific fault where the A960E automatic transmission exhibits a shudder or vibration at 45–65 km/h during light throttle cruising, most pronounced when the engine is cold or the transmission fluid is degraded. The root cause is premature engagement or slipping of the torque converter lock-up clutch. A specialised ATF fluid change (Toyota WS fluid) resolves it in mild cases; severe cases require torque converter clutch solenoid replacement or converter rebuild. Lexus issued technical guidance on fluid type as a first step.

• Vibration or judder felt through the floor and seat at 45–65 km/h at light throttle
• Shudder most noticeable in the first 5–10 minutes of driving when cold
• Symptom largely disappears at full throttle or highway cruise
• Smooth at low and high speeds but shudder in the mid-range cruise band

1. 1

   Test drive in mixed conditions, starting cold.

2. 2

   Drive at 50–60 km/h on light throttle and note any vibration through the floor.

3. 3

   Repeat after 10 minutes of warmup to compare.

4. 4

   Check transmission fluid condition — dark or dirty fluid makes the issue significantly worse.

Parts involved: Torque converter.

≈A$230 to ≈A$2,580 at independent workshop rates, shown as an approximate guide in Australian dollars. That is for this job on its own, not for the car.

An estimate, converted to Australian dollars, 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.

• “Have you ever noticed a vibration or shudder at about 50–60 km/h?”
• “Has the transmission fluid been changed recently with Toyota WS fluid?”
• “Has a transmission specialist looked at the car?”

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.