2018-2020 Lexus LC500 Torque Converter and 10-Speed Transmission Guide
Diagnosing shudders and harsh shifts in the LC500's Aisin 10-speed automatic transmission and understanding torque converter issues.
- There are no specific recalls or TSBs for the 2018-2020 LC500 torque converter; recalls for this vehicle primarily address fuel pump issues.
- Symptoms like harsh shifting or shuddering could be caused by the torque converter, but transmission software issues have also been reported and should be investigated first.
- Replacement is a major, expensive repair (5/5 difficulty) requiring complete transmission removal and is not recommended for DIY.
- When buying a used torque converter, physically inspect the hub for scoring and the splines for damage, and avoid any units showing signs of overheating (blue discoloration).
Symptoms of a Failing Torque Converter
A faulty torque converter can cause a range of transmission-related problems. While the 2018-2020 Lexus LC500 is not known for widespread torque converter failures, it's important to recognize the signs, as they can overlap with other transmission issues.
1. Shuddering or Vibration
This is the most common symptom. It may feel like driving over a rumble strip and often occurs at steady speeds, particularly when the transmission is about to shift or when the lock-up clutch is engaging. This can be caused by a worn-out lock-up clutch or contaminated transmission fluid.
2. Transmission Slipping
If you notice the engine RPMs flaring up without a corresponding increase in speed, the transmission might be slipping. While this can be caused by worn clutches inside the transmission, a failing torque converter can also be the culprit, as it may not be transferring power effectively.
3. Harsh or Delayed Shifting
Some owners of early model LC500s have reported issues with harsh shifting. While this could be a sign of a bad torque converter, it can also be related to transmission control module (TCM) software. A failing torque converter can cause delayed engagement when shifting from Park to Drive or Reverse, or clunky, hard shifts between gears.
4. Overheating Transmission
A failing torque converter can generate excessive heat, which can cause the transmission fluid to break down and lead to an overheating condition. Some owners have reported transmission overheating during aggressive or track driving. If you see a transmission temperature warning light, it's a serious issue that needs immediate attention.
5. Unusual Noises
A whining, whirring, or clicking sound that changes with engine RPM could indicate a problem with the needle bearings inside the torque converter. These noises are often most noticeable when the car is in gear and stopped.
6. Stalling at Idle
In severe cases, a problem with the lock-up clutch can cause it to remain engaged, which will stall the engine when you come to a stop, much like failing to press the clutch in a manual car.
Known Issues, TSBs, and Recalls for the 2018-2020 Lexus LC500
As of mid-2024, there are no specific recalls or Technical Service Bulletins (TSBs) for the torque converter on the 2018-2020 Lexus LC500.
The most prominent recalls for this vehicle concern a faulty low-pressure fuel pump that could cause the engine to stall. This is an engine issue, not a transmission one, but a stalling condition could be misdiagnosed.
Pro Tip: Some owners of early model year LC500s have reported harsh shifting, with at least one instance leading to a full transmission replacement under warranty at around 37,000 miles. Lexus also issued a TSB (L-SB-0039-18 Rev2) for the 2018-2020 LS500, which uses a similar 10-speed transmission, to fix harsh shifts and delays with a software update. If you experience these symptoms, a dealership visit to check for the latest transmission software is a logical first step before assuming a hardware failure.
Additionally, a TSB (L-SB-0002-20 Rev) exists to help technicians differentiate between a minor fluid "seep" and a more serious "leak" from powertrain components, which could include the transmission seals.
Buying a Used Torque Converter: What to Check
Since a new OEM torque converter can be expensive, a quality used unit from a low-mileage vehicle is a viable option. However, it's a part you cannot test before installation, so careful inspection is key.
- Verify Compatibility: Ensure the part number matches your vehicle's requirements. The OEM part number for the 2018-2020 LC500 torque converter is generally cited as 35610-11010.
- Inspect the Hub: The hub is the machined snout that fits into the transmission's fluid pump. It should be perfectly smooth and free of any scoring, deep scratches, or grooves. A damaged hub will destroy the transmission pump seal, causing a major leak.
- Check the Input Splines: Look inside the hub. The splines that engage with the transmission's input shaft must be sharp and well-defined. Any sign of twisting, rounding, or metal shavings is a major red flag.
- Examine Mounting Studs/Pads: Check the studs or pads that bolt to the engine's flexplate. Ensure the threads are clean and undamaged.
- Look for Signs of Overheating: Any blue or purple discoloration on the converter's shell is a clear sign it has been subjected to extreme heat. Avoid any converter that shows these signs, as the internal components are likely damaged.
- Source Vehicle History: Whenever possible, purchase a torque converter from a vehicle with documented low mileage and no history of transmission failure or accidents. A part from a car with a known transmission issue is likely to have the same problem.
Replacement Cost & Difficulty
Replacing the torque converter is a major repair because the entire transmission must be removed from the vehicle.
| Item | Estimated Cost |
|---|---|
| New OEM Torque Converter | $1,000 - $1,500+ (estimate) |
| Remanufactured Torque Converter | $350 - $700 |
| Used OEM Torque Converter | $250 - $500 |
| Shop Labor | $1,200 - $1,800 |
| Transmission Fluid & Filter | $150 - $300 |
| Total Professional Replacement | $1,700 - $3,600+ |
Warning: These prices are estimates. The Lexus LC500 is a high-performance luxury vehicle, and parts and labor costs can be significantly higher than for more common vehicles. Always get a detailed quote from a qualified repair shop.
Installation Difficulty: 5 out of 5
- DIY Feasible: No.
- Estimated Time: 8-12 hours.
This job requires a vehicle lift, specialized transmission jacks, a comprehensive set of tools, and expert-level mechanical knowledge. The transmission is heavy and difficult to handle. Improper installation, such as not seating the torque converter into the pump correctly, will cause immediate and catastrophic damage to the new part and the transmission pump.
Frequently Asked Questions (FAQ)
Is the harsh shifting in my LC500 a bad torque converter?
It could be, but it's not the only cause. Some early LC500s experienced harsh shifting that was sometimes addressed by a full transmission replacement under warranty. A similar Lexus model (LS500) had a software update to fix this exact issue. It's best to have a Lexus dealer check for software updates before condemning the torque converter.
Can I just replace the torque converter clutch (TCC) solenoid?
The TCC solenoid is typically located inside the transmission on the valve body. While replacing a solenoid is less expensive than replacing the entire torque converter, it still requires removing the transmission pan. If a diagnostic code specifically points to a solenoid circuit failure, this may be an option. However, shuddering is often caused by a worn clutch surface inside the converter itself, not just the solenoid.
What causes a torque converter to fail?
The most common causes are overheating, contaminated transmission fluid, and simple wear and tear on the internal bearings or lock-up clutch. Overheating is the biggest enemy, as it breaks down the fluid and can warp internal components. This is a greater risk with aggressive driving or on a track.
Do I need to flush the transmission when replacing the torque converter?
Yes, this is critical. If the old torque converter failed and sent debris into the system, that debris must be flushed out of the transmission cooler and lines. Failure to do so will cause the new torque converter and the rest of the transmission to fail very quickly. Most shops will insist on this as part of the replacement process.
Technical Specifications
OEM Part Numbers: 35610-11010
Fits the Aisin AWR10L65 10-speed automatic transmission.
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Lexus LC500:
- Symptoms of a Failing Torque Converter
- 1. Shuddering or Vibration
- 2. Transmission Slipping
- 3. Harsh or Delayed Shifting
- 4. Overheating Transmission
- 5. Unusual Noises
- 6. Stalling at Idle
- Known Issues, TSBs, and Recalls for the 2018-2020 Lexus LC500
- Buying a Used Torque Converter: What to Check
- Replacement Cost & Difficulty
- Installation Difficulty: 5 out of 5
- Frequently Asked Questions (FAQ)
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