Two truck owners just sued General Motors over the same transmission complaint owners have been filing for a decade. On its face, that is not news. Underneath, it is the clearest evidence yet of how a landmark federal appeals court ruling is quietly reshaping the way Americans sue automakers.
Matthew Barba and Renzo Calvo-Saez, two California men who each bought a new Chevrolet Silverado, filed a class action against GM this month alleging the company sold Sierra, Silverado, Canyon and Colorado trucks with a defective Hydra-Matic 8L90 or 8L45 transmission and hid what it knew. The case, Barba et al. v. General Motors LLC, was removed to the U.S. Distri
ct Court for the Eastern District of Michigan, case No. 4:26-cv-13030 — the same courthouse that has been hearing versions of this complaint since 2019.
That detail matters more than the headline defect.
Three years ago, a nearly identical case — Battle v. General Motors, filed in the same Michigan federal court in 2022 — grew into one of the largest active product-defect class actions in the country. Consolidated as Speerly v. General Motors, it eventually covered roughly 800,000 vehicles across 26 states: Camaros, Colorados, Silverados, Corvettes, Cadillac Escalades and CTS models, GMC Sierras and Canyons, and Yukons, all built with the same two transmissions. In March 2023, a federal judge certified the class. GM appealed, and in June 2025, the Sixth Circuit Court of Appeals — sitting en banc, its full bench rather than a three-judge panel — vacated that certification entirely.
Here is the part most owners never hear: the appeals court did not say GM’s transmissions were fine. It said the case had been argued the wrong way. The lower court, the majority held, had treated “defect” as one abstract idea rather than tracing exactly how each of 26 different states’ warranty, fraud and consumer-protection laws define it — a defect claim under California law does not prove itself the same way a defect claim under Ohio law does, and a judge cannot wave that away and sort it out later at the damages stage. Individual questions, like whether a specific owner ever brought the truck in for repair, or was bound by an arbitration clause buried in a sales contract, had to be resolved before certifying a class that size, not after.
That is the real story behind this month’s filing. The new Barba suit is not a fresh discovery. It is what litigation over this transmission looks like after the rulebook changed: instead of one certified class covering 800,000 trucks, plaintiffs’ firms are now filing narrower, state-specific cases — this one limited to California buyers of 2019 model-year trucks built after March 1 of that year. Shrinking the class is not retreat. It is compliance with a ruling that made the old approach unworkable.
A Decade of “That’s Normal”
The underlying complaint about the 8L90 and 8L45 transmissions has stayed remarkably consistent since GM introduced them for the 2015 model year: harsh, jerking downshifts, most noticeable at low speed and on a cold start. GM’s own published specifications show why the transmission family is stretched across such different jobs — the 8L45 is rated for as little as 275 lb-ft of engine torque in a Colorado, while the 8L90 in a heavy-duty Silverado handles up to 460 lb-ft, both routed through the same eight-speed architecture and adaptive-shift software.
That software is where the first surprise lives. GM’s own technical service bulletins — the documents dealers are required to follow — have told technicians for years that a hard first-shift-of-the-day “is a normal characteristic of the transmission,” and, in a bulletin reissued in October 2023, that “replacing transmission components will not correct the condition.” In plain terms: the fix GM authorizes its own dealer network to perform is to compare the customer’s truck to another one and send them home. Owners who assumed a mechanic was just being dismissive were, according to GM’s own paperwork, correct — there was nothing in the shop manual to fix.
The second thing worth knowing is how long GM sat with this. Court filings in the earlier Battle case cite internal GM testing from 2014 that described a hard downshift as a “neck snapper,” and describe the eight-speed program being flagged internally at “yellow” or “red” status for years afterward. GM did not rebuild the transmission’s hardware to address shift quality until the redesigned “Generation II” 8-speed arrived with the 2024 model-year Silverado and Sierra — nearly a decade after engineers first raised the concern internally, and five years after the trucks named in this month’s lawsuit were built.
Why This Keeps Happening
None of this makes GM unusual. It makes GM current. The same Sixth Circuit ruling that reshaped this case is already showing up in defense filings in unrelated vehicle-defect suits against other manufacturers, because federal circuits routinely look to their sister courts when deciding how rigorously to police class certification. The mechanism is bigger than one transmission: when a defect is real but its effect on each owner varies — one driver never notices a hard shift, another replaces a transmission at 60,000 miles — proving it as a single national case just got dramatically harder everywhere, not just in Michigan. GM has been here before: a 2025 recall of more than 721,000 V8-powered trucks and SUVs for a separate engine defect was followed by its own consolidated federal lawsuit over whether that recall actually fixed the problem.
That is a mixed result for owners. A single 800,000-vehicle class action is efficient, but it also tends to settle cheap on a per-vehicle basis and take years to resolve. A wave of smaller, state-specific cases is slower to build and harder to track, but each one has to prove its facts more precisely — and a plaintiff’s win under California law does not get diluted by also having to satisfy Ohio’s.
The transmission did not get fixed in September. The rulebook for suing over it did — and the size of this lawsuit is the proof.
Have you owned a GM truck or SUV with the 8-speed transmission — did a dealer ever tell you a hard shift was “normal”?