The National Highway Traffic Safety Administration (NHTSA) has closed a petition requesting a formal safety investigation into reports of all-wheel drive (AWD) failures affecting certain Acura TLX and MDX vehicles. While the agency acknowledged that the reported mechanical failure is real, it concluded there is currently insufficient evidence to classify it as a safety-related defect requiring a formal investigation or recall.
Which Vehicles Are Affected?
The petition involved:
- 2021–2023 Acura TLX equipped with Super Handling All-Wheel Drive (SH-AWD)
- 2022–2023 Acura MDX equipped with SH-AWD
According to the petition, a mechanical failure inside the drivetrain can prevent power from being sent to the rear wheels, effectively turning the vehicle into front-wheel drive only.
What Is Failing?
The reported issue involves the splined connection between the front transaxle and the Power Take-Off Unit (PTU). Over time, these splines can shear or strip, permanently disconnecting the rear drivetrain.
When this happens:
- The vehicle loses all rear-wheel drive capability.
- Power is sent only to the front wheels.
- The failure is permanent until repaired.
Interestingly, many owners reportedly did not realize anything had failed until driving on snow, ice, or another slippery surface where AWD traction would normally be expected.
Why Did Owners Want an Investigation?
The petition argued that losing AWD could reduce directional control and create a safety risk, particularly in poor weather conditions. The concern was heightened because Acura’s SH-AWD information display may continue to indicate that torque is being delivered to the rear wheels—even after the mechanical connection has completely failed. In other words, drivers may believe their AWD system is functioning normally when it is not.
What Did NHTSA Find?
NHTSA’s Office of Defects Investigation reviewed:
- 62 consumer complaints (Vehicle Owner Questionnaires)
- Manufacturer field reports
- Technical information about the SH-AWD system
The agency confirmed that the spline failure does occur and results in the permanent loss of torque to the rear axle.
However, investigators also found:
- The vehicles continue to operate normally as front-wheel drive vehicles.
- There is no loss of engine power.
- Vehicle Stability Assist (VSA) and traction control remain fully operational.
- The steering and braking systems continue to function normally.
Most importantly, NHTSA found no evidence that the failure causes drivers to lose control of the vehicle.
Why Was the Petition Denied?
NHTSA determined that Acura’s SH-AWD system is primarily a performance-enhancing feature rather than a critical stability system. Unlike some traditional AWD systems that are necessary for maintaining mobility after drivetrain failures, these Acura models are fundamentally designed as front-wheel drive vehicles. Because of that, the agency concluded that losing rear-wheel drive affects vehicle performance rather than basic vehicle safety.
The investigation also found:
- No reported crashes linked to the failure.
- No reports of loss of motive power.
- No documented injuries resulting from the condition.
Without evidence that the defect creates an unreasonable safety risk, NHTSA declined to open a formal defect investigation.
Does This Mean There Isn’t a Problem?
Not necessarily. NHTSA specifically stated that closing the petition does not mean a safety defect does not exist. Instead, it means the agency currently lacks sufficient evidence that the issue presents an unreasonable safety risk under federal safety standards. The agency also noted that it may reopen the matter if future complaints, crashes, or additional evidence emerge.
What Should Acura Owners Do?
If you own one of the affected Acura models, it is worth paying attention to any changes in how your vehicle performs, particularly during wet, snowy, or icy driving conditions.
Potential warning signs may include:
- Reduced traction on slippery roads
- Difficulty accelerating in snow
- Unexpected front-wheel spin
- Service messages related to the AWD system
Because the SH-AWD display may continue to indicate normal operation even after the drivetrain has failed, routine inspections by a qualified technician may be the only way to identify the problem before winter driving exposes it.
The Bottom Line
The reported SH-AWD spline failure is a genuine mechanical issue that can disable the rear-wheel drive system in certain Acura TLX and MDX models. However, after reviewing dozens of owner complaints and technical evidence, NHTSA concluded there is not enough evidence to show that the condition creates an unreasonable safety risk warranting a formal defect investigation.
For now, no recall has been issued, but the issue remains on NHTSA’s radar. Owners experiencing AWD performance problems should have their vehicle inspected promptly and consider reporting the issue to NHTSA, as additional reports could influence future agency action.
