New GM Tranny Class Action Suit, Tempest in a Teapot, Or…?

[AbleGuy]

Any Colorado or Sierra owners out there having lurching probs with your GM 8 spd? How real world common is this alleged transmission problem? Something to keep an eye on perhaps.

A new class action lawsuit claims unreasonable problems with some of the GM 8 speed transmissions used in several different models of vehicles. For this forum, it’s mostly the allegations involving the mid sized and full sized trucks you might be interested in following up on.

“A judge has granted class action certification to a lawsuit involving 39 plaintiffs across 26 states that accuses General Motors of knowingly selling cars with faulty transmissions.

On Monday, David Lawson, U.S. District judge for the Eastern District of Michigan, granted class certification in the case of Speerly v. GM, which represents the owners of various GM vehicles who have one of two models of eight-speed automatic transmissions — the GM 8L90 or 8L45 — made between 2015 and March 1, 2019.

Some drivers reported the gear shifting so violently that it felt as if they were hit by another car, Leopold said in a statement. The attorney for the plaintiffs also said internal company documents show that GM had determined the “startling effect” of the harsh shifts can create a safety issue. The vehicles also have a second transmission defect that causes them to “shudder” at highway speeds, the lawsuit said.”

The court order listed the following vehicles with the alleged faulty transmissions:

• 2015 through 2019 model year Chevrolet Silverado
• 2017-19 Chevrolet Colorado
• 2015-19 Chevrolet Corvette
• 2016-19 Chevrolet Camaro
• 2015-19 Cadillac Escalade and Escalade ESV
• 2016-19 Cadillac ATS, ATS-V, CTS, CT6, and CTS-V
• 2015-19 GMC Sierra, Yukon, Yukon XL, and Yukon Denali XL
• 2017-19 GMC Canyon
  
  
• https://www.autoblog.com/2023/03/21/gm-8-speed-automatic-class-action-lawsuit/

 

[ThundahBeagle]

The struggle is real. Not just the 8-speeds, either. My 2014 GMC Sierra 5.3 Liter Z71, 6 speed trans does it. Usually as I slow for a relight or traffic, place my foot on the brake gently, or then need to start accelerating. Seems all the moving parts can figure it out in unison.

And every time I bring it in for service and mention it, they say " they all do that" and put no documentation on my forms.

Make SURE you force them to document it and get an appointment specifically to have it checked. For me, a pan drop, new filter and new fluid seemed to help.

Tough part is, between u joint links, the AFM/ DFM kicking on and off, the regular tranny kickdown gear engaging on slowdowns and light acceleration, the contraption doesnt know whether it's coming or going.

Feels like a tap from behind from a Prius or Mini Cooper.

 

[ThundahBeagle]

Why they chose 2015 and up, I will never know.

 

[ChasingOurTrunks]

The problem with the GM 8-speeds is extremely noticeable and I would say fairly common. Over on Coloradofans, there are countless pages of posts on them. In general though, this lawsuit is focused on a very specific behaviour from what I understand, and that is a slipping torque converter (they think).

It manifests itself first as "rumbles" at speed; kind of like you are hitting the rumble strips on a highway that warn you of a stop sign ahead, every few seconds there will be a "purr" and a vibration that you can feel in the seat and floor of the vehicle. This then evolves into incredibly jagged shifting which does feel like getting rear ended from time to time.

There are other folks with transmission issues on the bandwagon of this particular problem, but they are rare -- the overwhelming majority of 8-speed problems appear to follow the pattern I've described above.

GM's first solution was to swap out torque converters and do a fluid flush, but the problem would re-appear. They have since gone through two different versions of Mobil-1 fluid for the transmission, and the most recent iteration seems to have addressed the challenges.

In terms of the cause, I think (but don't know for sure) that it has something to do with moisture in the fluid. This hydroscopic fluid theory has been around for a while, but anecdotally I never had problems at all with my Canyon until I relocated away from a dry climate to living on the coast, where the rumble started happening within about 60 days of being here. GM did a partial good-will warranty for us through a local dealer (We were out of warranty by a couple of months in terms of date, but about 100k kilometers left on the mileage figures) and did a full flush of the ATF, and filled it with the new spec of fluid for about a quarter the price that service would normally cost. So far no problems really; I find that my truck doesn't shift quite as smooth as I would like, but I can't say it's any different than it was before and...it's a truck, not a sports car, so a bit of personality to the shifting is not really a problem for me unless it is indicative of deeper problems.

The real challenge here from my perspective is that GM has been building transmissions for a LONG time, and ATF has been around for a long time, so what exactly is it about this transmission that is causing these problems and how has it taken literally years for GM to figure it out, if they even have? I would definitely describe this as unreasonable problems on a modern vehicle, but they aren't deal breakers on an otherwise excellent vehicle - it's not the kind of problem that would leave you stuck in the bush, it's the kind of problem that makes the highway drive home a bit annoying, and its an easy fix if all that needs to happen is a fluid swap. So, not a deal breaker for me and I wouldn't discourage anyone from looking at the Canyon/Colorado twins as an Overland platform.