Lexus NX: AC60F Torque Converter Clutch Shudder

The AC60F 6-speed automatic transmission fitted to AGZ NX models is susceptible to torque converter clutch shudder. The lock-up clutch engages at low vehicle speeds, typically 30-60 km/h, under light throttle, and worn clutch friction material or degraded ATF causes vibration felt through the cabin floor and seats. The shudder mimics a rough road surface or engine misfire. Toyota ATF WS fluid specification is critical; incorrect fluid or fluid degraded past service interval is the primary cause. Many cases resolve with a double drain-and-fill of Toyota ATF WS, though advanced friction material wear requires torque converter replacement.

• Vibration or shudder felt through floor or seat at 30-60 km/h under light throttle
• Shudder disappears under firm throttle or when fully coasting
• Sensation similar to driving over rumble strips at low speed
• Symptoms may worsen as ATF temperature rises to normal operating range

1. 1

   Drive the vehicle at 40-60 km/h on a smooth road under very light throttle and check for vibration through the seat or floor.

2. 2

   Check automatic transmission fluid condition and colour.

3. 3

   Confirm Toyota ATF WS specification was used at all prior service intervals.

4. 4

   If shudder is present, a double ATF drain-and-fill with genuine Toyota WS fluid should be the first remediation step before condemning the torque converter.

Parts involved: Torque converter, Clutch.

$350 to $4,000 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.

• “Has the automatic transmission fluid been changed and what fluid specification was used?”
• “Has any vibration or shudder been noticed at 40-60 km/h under light throttle?”
• “Has the transmission ever been serviced by a non-Lexus workshop?”
• “Has the torque converter or transmission been replaced or rebuilt?”

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.