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Author Topic: GM 8-speed automatic in rear-drive cars  (Read 516 times)

Offline jdemerson

  • 1952 Cadillac 6219X Vermont -- Emerson
  • Posts: 864
  • Very large collection of Cadillac sales brochures
  • CLC Number: 26790
  • Name: John D Emerson
GM 8-speed automatic in rear-drive cars
« on: September 25, 2019, 01:57:00 PM »
Another class-action lawsuit that involves several Cadillac models from 2015 to 2019.

Cadillac models potentially affected are: 

2015-2017 Cadillac Escalade and Escalade ESV
2016-2019 Cadillac ATS and ATS-V
2016-2019 Cadillac CTS and CTS-V
2016-2019 Cadillac CT6

Not what GM needs.

John Emerson
John Emerson
Middlebury, Vermont
CLC member #26790
1952 Series 6219X

Offline savemy67

  • Posts: 1364
  • Name: Christopher Winter
Re: GM 8-speed automatic in rear-drive cars
« Reply #1 on: September 25, 2019, 08:27:59 PM »
Hello John (and all),

"Specifically, the 18-NA-355 TSB addresses “torque converter clutch (TCC) shudder conditions” for the 8L45 and 8L90 eight-speed automatic transmission"

The above quote is from the article referenced in John's post.  My personal experience is that the TCC shudder issue goes back at least as far as the 4L80E in the mid-'90s.

It is ironic that a few replies to Doug Bailey's post elsewhere on this forum, regarding a leaky Hydra-Matic, urged Doug to consider a stop leak product as a last resort.  The TSBs addressing the TCC shudder issue include the use of a different transmission fluid that ostensibly corrects the problem.  I equate those TSB recommendations with "snake oil", because I don't believe the different transmission fluid is a long term fix for the TCC issue.  My proposal to fix the TCC issue is to modify the valve body by either eliminating the TCC valve spring (and disabling TCC) or reaming the valve body bore for a new TCC valve and spring.

Unfortunately, this is another example of a design/quality defect sold by GM.

Respectfully submitted,

Christopher Winter
Christopher Winter
1967 Sedan DeVille hardtop

Offline 64\/54Cadillacking

  • Posts: 798
  • Name: C.Asaro
Re: GM 8-speed automatic in rear-drive cars
« Reply #2 on: September 26, 2019, 01:31:14 AM »
I just don’t understand how GM could build reliable and strong smooth operating transmissions in the 60’s and 70’s with the TH400 and even the 4L60E starting in 1994, but yet make such unreliable ones today.

We all know parts are more complex these days, but I mean the company has been building transmissions for decades and the core design hasn't changed much just adding more gears to the unit. Or maybe more gears isn’t the best choice for long term reliability?
1964 Sedan Deville (Own)
1987 Brougham D’Elegance (Sold)
1954 Cadillac Fleetwood 60 Special
1994 Fleetwood Bro (Sold)
1972 Sedan Deville (Sold)
1968 Coupe Deville (Sold)
1978 Lincoln Continental (Own)
1979 Lincoln Mark V Cartier (Own)

Offline Gary McKinney

  • Posts: 95
  • CLC Number: 8951
  • Name: Gary McKinney
Re: GM 8-speed automatic in rear-drive cars
« Reply #3 on: September 26, 2019, 07:53:47 AM »
My 2018 CTS developed the shudder about a month ago.  It was explained to me that the original GM transmission fluid was hydroscopic, and the moisture caused slippage resulting in the shudder.  Who knows.  The system was flushed several times and refilled with a "new" Mobil 1 synthetic fluid that is (supposedly) not hydroscopic.  The shudder went away immediately, but who knows for how long.  The service manager told me that the fluid may need changed again at some point. 
Gary McKinney

1950 Cadillac Series 62 Coupe
1966 Cadillac Eldorado
2018 Cadillac CTS

Offline fishnjim

  • Posts: 2416
  • Name: J. Bozin
Re: GM 8-speed automatic in rear-drive cars
« Reply #4 on: September 26, 2019, 01:08:16 PM »
I don't think it's fair to solely blame for things that are in large part forced by govt CAFE standards.   If they could use the TH400, much heavier trans and vehicles, I'm sure it would be in there, but when you have to meet these "fleet" averages, you have to lightweight and add gears to improve efficiency.   It's not always as easy as people think, especially "just force them" politicians, that don't have any experience in manufacturing or engineering.   Not saying there can't be a design issue that needs to be solved or would better resolved it long term, but without all the facts, any internet chatter is premature.   
Cadillac has always been the "test grounds" for the new, as they are the high margin vehicles that can best tolerate any post delivery costs associated with new items.  Also why they cultivate customer loyalty.   Once proven and cost effective, those improvements trickle into the other lower cost brands.
Sounds to me, if the fluid change instantly solved the problem, then it's probably a good diagnosis and not "snake oil".   It maybe a stop gap for some clearance or other* more permanent issue, as alluded.  If they fix it "too good", it'll impact future sales.  "Maybe I can get another year out of it now?"    But how long is a company liable after the sale - usually only within warranty terms?   That would take much more time and cost to resolve, which is better to incorporate into new production.   Think of it this way, if it was your car, would you let them take it in and tear it apart to fix a small issue, and suffer the lost time?   From a  supplier perspective, they'd have to accommodate a lot of shop time, cost, loaners, and POed customers so will opt to do the least damage.
The "run around" however, is not tolerable for me.
No one wins, when the lawyers cash in.
* - I've been done in by purchasing a few times, you write a spec and they shop it, and "try" someone new, for cost, and it's not up to your expectations.   All part of the game, no different making cars.


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