GM 8‑Speed Transmission (8L45 / 8L90) — “Shudder”

GM’s 8-speed automatic transmissions (8L45 and 8L90) are known for torque converter clutch shudder, harsh downshifts, and fluid aeration. GM issued multiple TSBs and fluid reformulations to address the issue, but many vehicles continued to experience drivability problems. Issues:

Torque converter clutch (TCC) shudder
Harsh or delayed downshifts
Fluid aeration / foaming
Multiple TSBs and fluid reformulations
A class‑action lawsuit that is still moving forward LSX
A major fluid replacement campaign using a new Mobil 1 ATF GM Authority
GM acknowledging the issue through repeated TSBs Transmission Digest

These problems affected a wide range of GM vehicles from 2015–2022.

Year(s)	Make	Model	Should Purchase?	Reason	Notes
2015 2016 2017 2018	Chevrolet	Silverado 1500	Not Suggested	Torque converter shudder; harsh downshifts	Transmission: 8L90 Fluid aeration; multiple TSBs Vibration under light throttle
2015 2016 2017 2018	GMC	Sierra 1500	Not Suggested	Same 8L90 shudder issue	Transmission: 8L90 Requires updated fluid flush Harsh downshifts common
2015 2016 2017 2018 2019 2020	Chevrolet	Colorado	Not Suggested	Shudder and rough shifting	Transmission: 8L45 Smaller variant with same fluid aeration issue Known for torque converter slip
2015 2016 2017 2018 2019 2020	GMC	Canyon	Not Suggested	Torque converter clutch shudder	Transmission: 8L45 Often requires triple flush Harsh downshifts
2016 2017 2018 2019	Chevrolet	Camaro (V6)	Not Suggested	Shudder under light throttle	Transmission: 8L45 Vibration between 40–70 mph TSBs for fluid flush + reprogramming
2016 2017 2018 2019	Chevrolet	Camaro (V8)	Not Suggested	Torque converter shudder	Transmission: 8L90 Same fluid aeration issue as trucks Harsh downshifts
2016 2017 2018	Cadillac	ATS, CTS, CT6 (4‑cyl / V6)	Not Suggested	Luxury models still affected	Transmission: 8L45 Fluid aeration → torque converter slip Harsh downshifts
2016 2017 2018	Cadillac	ATS‑V, CTS‑V, CT6 V8	Not Suggested	Shudder even on performance trims	Transmission: 8L90 Multiple TSBs issued Vibration under steady cruise
2017 2018 2019 2020	Buick	LaCrosse, Envision, Regal	Not Suggested	Shudder and rough shifting	Transmission: 8L45 Same fluid aeration issue Requires updated fluid

Summary

GM’s 8-speed transmissions (8L45 and 8L90) used from 2015–2020 suffer from torque converter clutch shudder, harsh downshifts, and fluid aeration. GM issued multiple TSBs and reformulated transmission fluid several times, but many owners continued to experience drivability issues. These transmissions are generally not recommended for long-term ownership.