If you own a late-model GM truck, SUV, or certain year Corvettes and Cadillacs, with an eight-speed automatic transmission, you’re part of a class-action lawsuit. The lawsuit alleges the Hydra-Matic 8L90 or 8L45 automatic transmissions are defective. 

The list of alleged defects is long, as outlined by Carcomplaints. It says the transmissions “slip, buck, kick, jerk, harshly engage, suffer abnormal internal wear, sudden acceleration, delay in downshifts, delayed acceleration, and difficulty stopping the vehicle.” That or components therein must be replaced, according to the lawsuit. 

According to the lawsuit here are all of the vehicles affected:

The vehicles affected include the 2015-2019 Chevy Silverado, 2017-2019 Chevy Colorado, 2015-2019 Chevy Corvette, 2016-2019 Chevy Camaro. For the Cadillac brand, it affects 2015-2019 Escalade and Escalade ESV, 2016-2019 ATS and ATS-V, 2016-2019 CTS and CTS-V, 2016-2019 CT6. From the GMC line, it affects the Sierra, Yukon Yukon XL, Yukon Denali XL, and 2017-2019 Canyon. 

The suit goes on to say that the jerking, shaking, etc., are a result of internal transmission problems. There are issues either in the case or torque converter. It alleges these are safety hazards as well as costing owners expensive repairs.

Does issuing over 60 technical service bulletins mean GM knew there were problems?

According to the lawsuit, GM issued more than 60 technical service bulletins and updates related to these issues and complaints. So as a result, GM knew about the problems starting in September 2014. The lawsuit asks that GM replace all of the transmissions with non-defective transmissions. It also asks that the courts require GM to reform how its warranties. It wants to see issues covered like this, and want GM to recall all of the listed vehicles. 

Interestingly, it also includes two complaints from 2015 Corvette owners. The first, “8-speed automatic transmission downshifts at a stop with such force it feels as you have been hit from behind by another car coming to a stop. The transmission also will not always engage properly and will over-rev and slam into gear possibly causing an accident. Transmission at times will disengage while going forward then slam into gear with great force.”

Another 2015 Corvette owner complaint from the lawsuit:

And the second, “8-speed automatic transmission always shifts erratically when starting out cold (lazy shift, slow shift, etc.). Occasionally does not downshift when the car comes to a stop, only to slam hard into 1st when the gas pedal is pressed to resume travel. Dealer says GM claims this is “normal,” but no car I’ve ever owned behaves like this. Appears to be fluid starvation internally.”

Finally, the plaintiffs ask that owners be awarded “actual, compensatory, exemplary, and statutory damages. This would include interest, damages for economic loss including loss of the benefit of the bargain, overpayment damages, diminished value, and out-of-pocket losses.”