Understanding the SH-AWD System in the 2018 Acura RLX

The Super Handling All-Wheel Drive (SH-AWD) system is one of Acura’s most advanced drivetrain technologies, designed to enhance vehicle stability, handling, and overall driving performance. Introduced to maximize traction and cornering capability, the SH-AWD system in the 2018 Acura RLX dynamically distributes power not only between the front and rear axles but also between the left and right rear wheels.

This torque vectoring capability allows the RLX to maintain better grip during cornering, improve acceleration, and increase driver confidence under various driving conditions. Unlike traditional all-wheel-drive systems, which primarily split torque front-to-rear, SH-AWD actively manages torque side-to-side at the rear axle to reduce understeer and improve agility.

Key Components of the SH-AWD System

  • Center Differential: Distributes torque between the front and rear axles based on driving conditions.
  • Rear Differential with Torque Vectoring: Uses electronically controlled clutch packs to send varying torque to the left or right rear wheel.
  • Electric Actuators and Sensors: Monitor wheel speed, steering angle, throttle input, and yaw rate to calculate optimal torque distribution.
  • Vehicle Stability Assist (VSA) System Integration: Coordinates with SH-AWD to maintain vehicle control during slippery or aggressive driving situations.

The Importance of Proper Maintenance for SH-AWD

Because SH-AWD is a complex, electronically controlled drivetrain system, maintaining it properly is essential to ensure its longevity, reliability, and performance. Failure to perform routine maintenance can lead to premature wear of drivetrain components, reduced fuel efficiency, and compromised handling characteristics.

Moreover, the SH-AWD system relies heavily on the health of the transmission and rear differential. Neglecting fluid changes or ignoring warning signs can result in costly repairs or even total drivetrain failure.

Common Symptoms of SH-AWD System Issues

  • Unusual noises such as whining, grinding, or clunking coming from the rear differential or transmission area.
  • Warning lights on the dashboard, including the VSA or AWD system indicators.
  • Reduced traction or instability during cornering, especially on slippery surfaces.
  • Vibrations or shuddering sensations during acceleration or deceleration.

Routine Maintenance Procedures for the SH-AWD System

1. Transmission Fluid Inspection and Replacement

The transmission fluid plays a vital role in lubricating and cooling the components of the front differential and transmission, which are integral to the SH-AWD system. Acura recommends checking the transmission fluid level and condition regularly, especially if driving in severe conditions such as heavy traffic, mountainous terrain, or extreme temperatures.

Fluid Change Interval: For the 2018 Acura RLX, the transmission fluid should generally be replaced every 30,000 to 60,000 miles depending on driving conditions. Refer to the owner’s manual for specific intervals.

Fluid Type: Use only Acura-approved transmission fluid to maintain optimal system performance and prevent damage.

2. Rear Differential Fluid Service

The rear differential in the SH-AWD system is critical as it manages torque vectoring between the rear wheels. The differential fluid lubricates the gears and clutch packs inside the differential housing.

Inspection: Check for any leaks or contamination during regular service intervals.

Replacement Interval: Acura recommends changing the rear differential fluid every 30,000 miles to maintain proper lubrication and prevent wear.

Using the correct fluid type is crucial, as the rear differential uses a unique synthetic fluid designed for high-temperature operation and clutch pack engagement.

3. Tire Maintenance and Rotation

Tires are the interface between the SH-AWD system and the road. Uneven tire wear or mismatched tire sizes can cause the SH-AWD system to work improperly or trigger warning lights.

  • Maintain proper tire pressure according to Acura specifications.
  • Rotate tires every 5,000 to 7,500 miles to promote even wear.
  • Replace tires in sets to ensure consistent tread depth and rolling circumference.
  • Use only tires recommended for the RLX’s size and performance specifications.

4. Software Updates and System Diagnostics

Modern SH-AWD systems rely on sophisticated software to optimize torque distribution. Acura periodically releases software updates to improve system responsiveness and resolve known issues.

  • Have your vehicle scanned at authorized Acura service centers during regular maintenance visits.
  • Update the SH-AWD control module software as recommended.
  • Diagnose and address any fault codes promptly to avoid further damage.

Advanced Maintenance Tips for SH-AWD Longevity

1. Monitor Driving Habits

Aggressive driving, such as hard cornering, sudden acceleration, or frequent driving on rough terrain, places additional stress on the SH-AWD system. Moderating driving style can extend the life of drivetrain components.

2. Avoid Prolonged Idling and Excessive Towing

Extended idling or towing loads beyond the vehicle’s capacity can cause overheating and premature wear of the transmission and differential components.

3. Inspect Suspension and Wheel Alignment

Since SH-AWD works closely with the vehicle’s stability control and traction systems, proper suspension condition and wheel alignment are necessary for optimal performance. Misalignment or worn suspension parts can negatively affect SH-AWD efficiency.

Troubleshooting Common SH-AWD Problems

1. AWD Warning Light Illuminates

If the AWD warning light comes on, it may indicate a problem with the SH-AWD system or related sensors. Immediate steps include:

  • Safely pull over and turn the vehicle off, then restart to reset minor glitches.
  • If the light remains on, schedule a diagnostic check at an Acura service center.
  • Do not ignore the warning, as continued driving may cause further damage.

2. Unusual Noises from Rear Differential

Grinding or clunking noises may indicate worn gears or low differential fluid. Have the differential inspected and serviced promptly.

3. Reduced Traction or Handling Performance

Inconsistent traction or instability during cornering could be caused by worn tires, incorrect tire pressure, or malfunctioning SH-AWD components.

When to Seek Professional Help

Many maintenance tasks such as fluid changes and tire rotations can be performed by knowledgeable vehicle owners or local shops. However, because SH-AWD is a complex system, specialized tools and expertise are often required for accurate diagnostics and repairs.

Always consult with certified Acura technicians for:

  • Electronic system diagnostics and software updates.
  • Major repairs to the transmission or rear differential.
  • Replacing SH-AWD specific components such as the rear differential clutch packs.

Summary and Best Practices

The SH-AWD system in the 2018 Acura RLX is a remarkable technology that enhances driving dynamics by intelligently distributing torque to optimize traction and handling. Maintaining this system properly involves a combination of regular fluid changes, tire upkeep, software updates, and attentive driving habits.

By following Acura’s recommended maintenance schedule and addressing any issues promptly, owners can enjoy the full benefits of SH-AWD while minimizing repair costs and maximizing vehicle longevity. Routine inspections and professional servicing are essential to keep the system operating smoothly under all conditions.

Additional Resources