This should be deleted and have them start over with one post for each problem. This post is convoluted.

We're already well aware of this one. I never thought I'd see the day when GM says [We refuse to fix these transmissions under warranty because warranty coverage is solely for fixing manufacturing defects. These transmissions are of poor design, which is not a factory defect.]

If it were my turn to talk to GM about this, I'd ask where in the brochure does GM showcase the poor design of their transmission.

Looks like they quite separately came up with the same answer. Cool! Like a forum alliance or something.

Please check out this post in the site rules section: https://www.gmforum.com/introduction...7/#post1627535

I understand that you want to get lots of answers, but this puts members in the position of chasing down multiple threads for the same issue only to discover that it'* a duplicate.

. . . except the accurate factory-published answer.

They've already been combined. You won't be able to do this.

This should help:


Yes, I agree.

Except: The procedure to check level clearly identifies that it should be checked at normal operating temperature. Instead of making all of us look for what that specification is, they kindly included it right there with the level-checking procedure.

So far I only see one problem, summarized as being similar to the issues that many of these 8L transmissions have.

I think it has been figured out as of this post: https://www.gmforum.com/gmc-chevrole...2/#post1646204

This response was actually helpful, thank you! Somehow I missed that. Definitely helpful, also curious what others with similar truck run at typically.

Hopefully some folks that have these will post here. I think the 8-speed has been the "other" transmission for long enough now that most owners either have the ones that act okay, they don't care about the problems, or traded them by now.

I've rented a bunch of vehicles over the years with this transmission family, and they were all pretty good. I did see a few behaviors that made me lift an eyebrow, but very rarely. I'm not attempting to diminish whatever issues yours is having, just saying I've had a bunch of experience with a bunch of them and it'* been pretty good. All of mine were within probably 40,000 miles old.

The funny thing is: The various lawsuits document the various problems and GM says [it'* just a bad design, that'* how they work]. If they were all or mostly that way then I'd agree, but they're not. There are so many on the road that are okay enough that I'm amazed GM can get away with saying that this is a design issue. For this one, I would expect the following scene:

Plaintiffs' lawyer: GM, how many of these did you build?
GM lawyer: We have built over two million of them.
Plaintiffs' lawyer: How many had this problem?
GM lawyer: Less than 300,000.
Plaintiffs' lawyer: So what you're saying is that this transmission is designed poorly, and yet 85% of them work fine. Seems like that design isn't so bad after all. How is this NOT a warranty issue?

The other thing that I find funny about this is that, on countless documented occasions, GM attempted to fix these units. That appears to be a de facto agreement that [name the behavior] is improper and unexpected, therefore the design must not be bad. Did they ever, on any other significant number of cars, try to fix the transmissions when there were no problems found? I bet they didn't. If they did, it should be easy for them to prove; they'd need to look for service reports that identify [no trouble found] and also [attempted repair by doing X, Y, and Z].