GM Transmission Troubles: 6-Speed, 8-Speed, & 10-Speed Transmissions

Transmission problems have become a recurring issue for General Motors (GM) vehicles, affecting models equipped with 6-speed, 8-speed, and even the newer 10-speed transmissions. These issues range from rough shifting and delayed acceleration to dangerous shuddering and lurching, leaving many drivers frustrated and concerned for their safety. Despite GM’s attempts to address these problems through technical service bulletins (TSBs), new transmission fluids, and even class-action lawsuits, the scope and severity of the defects remain a significant issue.

At The Barry Law Firm, we are dedicated to helping Southern California consumers hold automakers accountable for selling defective vehicles. If you’ve experienced repeated transmission issues with your GM vehicle, you may be entitled to compensation under California’s Lemon Law. Read on to learn more about the most common transmission problems in GM vehicles and how we can help you protect your rights.

6-Speed Transmission Issues

The 6-speed automatic transmission in many GM vehicles, such as the Chevrolet Silverado and GMC Sierra, is notorious for its mechanical and performance failures. These issues can severely impact the driving experience, leaving drivers with unreliable and unsafe vehicles.

Common Problems with 6-Speed Transmissions

1. Hard Shifting: Many owners report difficulty shifting gears, particularly when the transmission is cold or transitioning between 2nd and 3rd gear. This issue may stem from worn clutch plates, a malfunctioning solenoid, or low transmission fluid levels. Hard shifts can make driving uncomfortable and put unnecessary strain on the transmission, potentially leading to further damage.
2. Whining Noise: A high-pitched whining sound often signals worn gears, bearings, or a failing torque converter. This noise can worsen over time, indicating a significant mechanical problem that requires immediate attention.
3. Slipping Gears: If your vehicle struggles to stay in gear or slips unexpectedly, it may be due to damaged clutch plates, a failing solenoid, or inadequate transmission fluid. This issue can be dangerous, especially when accelerating or driving on highways.
4. Fluid Leaks: Transmission fluid leaks are common and can result from damaged seals, gaskets, or cracks in the transmission case. Low fluid levels due to leaks can exacerbate other transmission problems, such as slipping gears or delayed engagement.
5. Delayed Engagement: A hesitation when shifting into gear, particularly from a stopped position, is another common complaint. This issue can make it difficult to drive smoothly or safely, especially in stop-and-go traffic.

Impact on Drivers

These recurring problems often require expensive repairs and can significantly reduce the lifespan of the transmission. If you’ve experienced any of these issues with your 6-speed GM transmission, you may qualify for relief under California’s Lemon Law, which protects consumers from defective vehicles that cannot be repaired after a reasonable number of attempts.

8-Speed Transmission Issues

The 8L45 and 8L90 eight-speed automatic transmissions have been the subject of widespread complaints and multiple lawsuits, with drivers reporting serious performance issues that impact safety and drivability. These transmissions, used in popular GM models such as the Chevrolet Silverado, Cadillac Escalade, and GMC Sierra, are known for their chronic defects.

Common Problems with 8-Speed Transmissions

1. Shuddering and Harsh Shifts: One of the most common complaints is a noticeable shudder during acceleration or deceleration, along with harsh shifts between gears. This is particularly common between 1st and 2nd gear and under light or medium throttle.
2. Hesitation and Lurching: Drivers have reported instances where the vehicle lurches forward or hesitates unpredictably, often described as feeling like being rear-ended. These abrupt movements can be dangerous, especially in heavy traffic or intersections.
3. Highway Shuddering: At higher speeds, vehicles equipped with 8-speed transmissions often exhibit shuddering or vibrations, making long drives uncomfortable and potentially unsafe.
4. Safety Hazards: Sudden lurching, delayed deceleration, and unpredictable shifting make these transmission issues more than just a nuisance—they pose serious safety risks to drivers, passengers, and other road users.

GM’s Efforts to Fix the Problem

To address these issues, GM introduced a new Mobil 1 Synthetic LV ATF HP transmission fluid in 2019. A fluid flush using this new formula has been shown to alleviate some of the shuddering and harsh shifting problems. However, this solution is far from universal—many drivers report that the fluid flush provides only temporary relief or fails to resolve the issue altogether. In such cases, GM’s recommended next step is to replace the torque converter, a costly repair that some owners have had to cover out-of-pocket.

If you’ve experienced ongoing issues with your 8-speed transmission, it’s important to know that you have legal options. California’s Lemon Law may entitle you to a refund, replacement vehicle, or other compensation.

10-Speed Transmission Issues

While GM’s 10-speed automatic transmission was introduced as an improvement over the problematic 8-speed, it has not been without its own issues. These transmissions are found in many newer GM vehicles, including full-size trucks and SUVs.

Common Problems with 10-Speed Transmissions

1. Rear Wheel Lockup: A major recall was issued for some diesel models equipped with the 10-speed transmission due to the risk of rear wheel lockup. Excessive wear in the transmission was identified as the cause, prompting GM to implement software updates to limit the transmission to 5th gear as a temporary fix.
2. Rough Shifting: Some owners report jerky or harsh shifts, particularly under load or when towing heavy cargo. While less frequent than the 8-speed issues, these complaints highlight ongoing reliability concerns.
3. Delayed Gear Engagement: Like the 6-speed and 8-speed transmissions, the 10-speed has also been known to exhibit delays when shifting into gear, creating safety concerns for drivers merging into traffic or pulling out of driveways.

While the 10-speed transmission is generally considered more reliable than the 8-speed, the ongoing complaints and recalls suggest that GM has yet to fully address transmission reliability in its vehicles.

Legal Action Against GM

General Motors (GM) is currently at the center of multiple class-action lawsuits and legal battles over widespread transmission defects in its 6-speed, 8-speed, and 10-speed automatic transmissions. These lawsuits allege that GM knowingly sold vehicles with defective transmissions, putting profit ahead of customer safety and satisfaction. For affected vehicle owners, these legal actions represent an opportunity to hold GM accountable and seek compensation for their losses.

Certified Class Action for 8-Speed Transmissions

In March 2023, a federal court certified a class-action lawsuit involving GM’s 8L45 and 8L90 eight-speed transmissions. The plaintiffs in this lawsuit allege that GM sold vehicles with defective transmissions that cause shuddering, lurching, delayed acceleration, and harsh shifts, creating dangerous driving conditions.

The court certified the lawsuit to represent owners in 26 states, including Florida, Texas, California, and Michigan. This certification means the court found enough evidence to allow the lawsuit to proceed as a group action, which enables thousands of affected vehicle owners to pursue damages collectively.

The plaintiffs accuse GM of:

• Failing to Disclose Known Defects: Evidence suggests GM was aware of the transmission issues as early as 2015, issuing more than a dozen Technical Service Bulletins (TSBs) to dealerships about the problem. However, customers were often told by dealers that these issues were “normal” for the vehicle.
• Deceptive Marketing: GM marketed its eight-speed transmissions as providing “world-class performance” and “lightning-fast shifts,” but customers experienced the opposite—frequent shuddering, hesitation, and abrupt, jarring shifts.
• Partial Fixes: GM introduced a transmission fluid flush (Mod1a) in 2019 to address shuddering issues, but the fix was not applied to all affected vehicles. Plaintiffs allege GM chose to limit the repair to specific vehicles under warranty, leaving many owners unaware of the fix or forced to pay out-of-pocket for costly repairs.

The class-action lawsuit seeks compensation for vehicle owners, including reimbursement for repair expenses, diminished vehicle value, and financial losses caused by the defect.

Expanded Lawsuit for Post-2019 Vehicles

In addition to the certified class-action lawsuit, another major lawsuit, Ulrich, et al. v. General Motors, has been filed to address transmission issues in vehicles manufactured after 2019. This lawsuit expands the claims to cover vehicles equipped with 8-speed transmissions sold in 10 additional states, including California, Missouri, and Massachusetts.

The Ulrich lawsuit also highlights GM’s alleged cost-cutting decision to avoid a full recall of affected vehicles. According to court filings, GM developed the Mod1a fluid flush in 2018 as a solution for the transmission issues. However, instead of recalling all vehicles to address the defect, GM limited the fix to unsold vehicles and those still under warranty, leaving millions of customers without a remedy.

The lawsuit accuses GM of:

• Negligence: Selling vehicles with known defects that could cause hazardous driving conditions, including sudden lurching, delayed acceleration, and unpredictable shifting.
• Lack of Transparency: Failing to inform customers about the defects or provide them with access to the fixes GM had already developed.
• Unfair Costs: Many customers were forced to pay out-of-pocket for repairs or transmission replacements once their warranties expired.

Legal Allegations: Safety Hazards and Consumer Deception

Both lawsuits emphasize the safety risks associated with GM’s defective transmissions. Drivers report situations where sudden lurching, hesitation, or delayed deceleration made it difficult to control their vehicles, especially when merging into traffic or braking in emergencies. Some drivers even compared the harsh shifting to being rear-ended. These dangerous conditions have led to accidents and near-misses, putting drivers, passengers, and other road users at risk.

Additionally, plaintiffs argue that GM’s failure to disclose the transmission defects before selling these vehicles constitutes consumer fraud. GM allegedly marketed these vehicles as reliable and high-performing, while concealing serious mechanical flaws that could diminish their value and compromise safety.

How The Barry Law Firm Can Help

At The Barry Law Firm, we specialize in helping California consumers navigate Lemon Law claims against automakers like GM. If your vehicle has experienced recurring transmission issues—whether it’s a 6-speed, 8-speed, or 10-speed model—you may be entitled to compensation, including a replacement vehicle or a refund.

Why Choose Us?

• Proven Expertise: We’ve helped thousands of clients successfully resolve Lemon Law cases, securing millions of dollars in compensation.
• Comprehensive Support: From evaluating your case to negotiating with GM, we handle every aspect of your claim.
• Personalized Service: Every case is unique, and we’ll work closely with you to develop a strategy tailored to your situation.

Don’t Wait—Contact Us Today

If your GM vehicle has been plagued by transmission problems, don’t wait to take action. The Barry Law Firm is here to help you protect your rights under California’s Lemon Law.

Contact us today for a FAST & FREE consultation to learn more about your legal options. You don’t have to deal with transmission troubles alone—let us fight for the justice and compensation you deserve.