2019 T1 8 speed Shifting

[bearded_warrior]

3 minutes ago, dj13990 said:

Thanks for the update. Sorry to hear they haven't done anything yet. I haven't had it happen again, fingers crossed.   Maybe the more of us that report the issue the more GM will do.  Please keep us posted on anything you do or if GM does anything else.  

Will do buddy. Good luck with your case too! 

[HondaHawkGT]

On 6/8/2019 at 12:11 PM, bearded_warrior said:

Unfortunately I have nothing good to report and it's back in my possession. 

 

TLDR; I think I have to go lemon law, I've had it in the shop two times (Going back Monday), 25 days, and have a safety concern because the transmission will lurch hard making it feel like you were rear-ended causing a hard whiplash feeling and the car jumps forward. Zero Support from GM TAC Case, no work authorized unless dealership can repeat with computer hooked up. 

 

Dealership has put ~350 miles on the truck and is unable to repeat any conditions besides what is defined in the TSB for hard 1-2 after start. I've had the truck back since Tuesday and driven it twice. (I've been using the motorcycle to get around) 

 

Here's what I logged from my 2.5 hour round trip commute on Thursday. (Sloppy voice to text notes)

 

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• Hard 1st to 2nd at 8:12 a.m. temperature is 185 degrees Fahrenheit today is June 5th. From stop steady throttle No hard acceleration Auto Stop disabled. Was driving for approximately 50 minutes
• Rough shift 1st to 2nd 8:20 a.m. fluid temperature 183 degrees Fahrenheit same conditions above
• Very hard shift first to second 154 degrees Fahrenheit transmission fluid at 3:53 p.m. external temperature 84 degrees driving time 20 minutes approximately 2500 to 3,000 RPMs

------

 

But wait... There's more, the truck lurched again today coming to a stop at a crosswalk. I'm completely out of ideas of what to do here or what it could be that's causing all this. 74 degrees outside, 25-30 min drive time, 155 degrees transmission temp. Ran into the store for 5 min and was leaving the shopping center. 

 

 

 

Side note; dealership has been very understanding and impressively dedicated to trying to repeat these issues. GM customer care has tried their best and my Customer Care Rep has been awesome,  but she literally cannot do anything else.  The District Manager is not doing anything until there is a repair attempt, which GM won't authorize.

 

I miss manuals. 

The lurch is also known as a "bump downshift". It's mainly become an issue with newer transmission designs that are trying to squeeze as much efficiency as possible out of the powertrain. When you are coming to a stop, the fuel is cut off as much as possible and the torque converter clutch stays locked up as long as possible. It can kind of get clunky as the vehicle stops. It's been an issue with the GM 6 and 8 speed transmissions, Ford F-150 10-speeds, and early Ram 1500 8-speeds. It's exacerbated by the fact that our trucks use a leaf-spring rear suspension and slip-yoke that can make a bump downshift feel harder due to the fact that the suspension can almost "wind up" and then suddenly release that energy.

 

One tip I was given a while back for helping clunky decal is by "teaching" the transmission. You can help your 8-speed "adapt" and downshift smoother when slowing to a stop by getting the truck up to 20-25 MPH and letting it coast to a stop without touching the brakes. Let the transmission downshift. It should get smoother and smoother each time you do this coast-down.

Edited August 11, 2019 by HondaHawkGT

[bearded_warrior]

10 hours ago, HondaHawkGT said:

The lurch is also known as a "bump downshift". It's mainly become an issue with newer transmission designs that are trying to squeeze as much efficiency as possible out of the powertrain. When you are coming to a stop, the fuel is cut off as much as possible and the torque converter clutch stays lock up as long as possible. It can kind of get clunky as the vehicle stops. It's been an issue with the GM 6 and 8 speed transmissions, Ford F-150 10-speeds, and early Ram 1500 8-speeds. It's exacerbated by the fact that our trucks use a leafspring rear suspension and slip-yoke that can make a bump downshift feel harder due to the fact that the suspension can almost "wind up" and then suddllenly release that energy.

 

One tip I was given a while back for helping clunky decal is by "teaching" the transmission. You can help your 8-speed "adapt" and downshift smoother when slowing to a stop by getting the truck up to 20-25 MPH and letting it coast to a stop without touching the brakes. Let the transmission downshift. It should get smoother and smoother each time you do this coast-down.

Thanks for this! Best explanation I've seen. 

 

Regarding the decel, any advice on how many times? And being that I am commuting into city traffic with constant stop and go, would the transmission "unlearn" the coast to stop. 

[bearded_warrior]

Went for a ride with the service manager today, we had some strange 1-2 behavior which we were able to repeat, unfortunately we couldn't get the downshift to happen again. It's totally random when it does happen so trying to repeat with the ride along was a total shot in the dark, but it was worth a shot.  Problem is still that unless we can repeat on command GM won't authorize any "repairs". 

[HondaHawkGT]

10 hours ago, bearded_warrior said:

Thanks for this! Best explanation I've seen. 

 

Regarding the decel, any advice on how many times? And being that I am commuting into city traffic with constant stop and go, would the transmission "unlearn" the coast to stop. 

 

I'm not sure what your long-term outlook would ve with a lot of stop-and-go driving. My driving is roughly 80% highway 20% city and I don't have any shifting issues other than the normal 1-2 clunk first tume it shifts in the morning. It sucks when something is intermittent like your issues. Tough to disgnose something like that when it's not consistsent or repeatable.

[bearded_warrior]

Does anyone know how to repeat the "Downshift Bump"?  I need to get that to happen with the service manager, it's so random when it happens, I have no idea what triggers it. I can't get any support from GM unless the dealership can reproduce. 

 

They are ignoring the hard upshifts that happened during the ride along too. 

 

I'm going for a 2nd opinion at another dealership this Friday, maybe i'll get lucky and it'll do it for them. 

Edited June 11, 2019 by bearded_warrior

[aggieguy03]

I’ve always tried to brake in a way that when I finally stop, you can’t tell that I stopped. My wife for example, will drive and brake all the way to the stop, and it lurches forward a bit. Whereas I will brake, and let up quite a bit right before it stops completely to soften it, almost as if I was still rolling. I don’t know that I explained that well in writing, so I hope that makes sense. This behavior comes from driving 1982 Thomas buses in college and not wanting to throw people into the seat in front of them lol

 

Well, I think that method of braking causes me to experience that lurch you are talking about. Where I think I’m stopped, but the truck thinks I still had another 1-2 mph to clear off the speedometer. It does not seem as if it’s as drastic as what you are describing, but it happens frequently on some trips and never on most trips. Cold or hot, doesn’t matter. There doesn’t seem to be any rhyme or reason to when it happens. It’s not enough frequency to bring it to the shop, but I’ll monitor. I’m about to roll 3700 and it’s definitely gotten better since I bought, so I’l do believe the tranny is always learning my driving habits. 

 

I’m 80/20 highway/city if that helps. 

 

Hope you get it figured out, keep us posted!

[SierraScreech]

I find that the rough downshift 2-1 is more apparent when having to stop while going down a slight hill and breaking lightly.

[bearded_warrior]

Thanks for the feedback, I haven't been able to reproduce the downshift yet but I had another jumpy/lurchy upshift that made me check my mirrors again in a parking lot. 

 

Initial trans temp about 65 degrees this morning at startup. Drove it about 15-20 minutes, then it sat for an hour, when the bad shift happened it was 111 degrees.  Smelled fuel about 30 seconds after this happened when I pulled out to the highway, I wasn't sure if it was my car or someone else, smell was strong and enough to warrant a trip by the dealership since I was already passing it. After I got there we came back to the car and I couldn't smell it anymore, we drove it around a bit and didn't see any leaks so maybe it was some other vehicle that had some potent fumes and bad timing.

 

 

[bearded_warrior]

My new favorite comment from GM in regards to my appointment tomorrow at another dealership for a second opinion (3rd Attempt). This was not from my good Customer Care representative. 

Quote

 As a heads up, if they too are unable to duplicate the concerns that you have with the vehicle, there is a likely possibility that the vehicle is operating as designed and no further repairs will be needed at this time.

[Sierra Dan]

AFM/DFM also affect how the transmission shifts and vice versa.

This has been a well discussed topic on the K2 side of the forum.

 

 

[ShamrockShooter]

2019 trail boss 5.3 8 speed, 2400 miles. Noticed my first very hard downshift. Think it was 2 to 1. Was coasting to a stop because of traffic. Didn't really have foot on the brake, was almost stopped when Wham-O it downshifted hard enough that I checked my mirror because I thought someone had hit me from behind.

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[bearded_warrior]

Got it back last week from the 2nd opinion 3rd Repair Attempt. Same unable to repeat and referenced the "Normal" 1-2 shift TSB.  Had a road trip and put 1k miles on it. Did great on the highways but as soon as I got off the highways it started clunking around. Nothing as aggressive as before, but we all know that happens randomly. 

 

Sorry I haven't been able to find anything yet, still working through it. Interested to hear if anyone else has had any luck.

[wizard4878]

On 5/10/2019 at 4:23 PM, econometrics said:

This is why I am not even going to bother to take my truck in for service on the 8 speed. 

 

Sure, I notice a few odd shifts from time to time, but after 1600 miles now, I really feel like it's smoothing out a lot. 

 

I honestly think a big part of it is me not attempting to notice every little harsh shift by paying special attention to it. As I have just stopped thinking about it and enjoyed the truck, I've noticed it less. Sometimes I think we can all be a little hypochondriac with our new, expensive trucks. ;) 

yes,  what he said^^^^^^^^^^^

most of us are super sensitive about a new vehicle

[bearded_warrior]

22 minutes ago, wizard4878 said:

yes,  what he said^^^^^^^^^^^

most of us are super sensitive about a new vehicle

I understand what you're saying here. but this leads to no resolutions and follows the BS TAC Case GM is spitting out with the "Normal Hard Shift and no degradation to your vehicle over time".

You quoted something prior to the video post where @econometrics also said that what I've documented is worth a look at. I can guarantee it's not normal. 

Quote

 

Yeah, it’s most definitely not acceptable for this to be a transmission “update” and still have the same issues the K2 8 speed did. I’m not very satisfied with that, either. Bad QA. 

 

Best advice I can give to help us all: Please, if you see something say something. if you say nothing, nothing will happen to improve or fix any issues for the rest of us.

 

@wizard4878 Great, i'm happy you aren't having issues, or if you are, they are not bad enough to talk to someone, but that's not helpful to those of us that are. Watch the jerkiness of the videos first please and acknowledge other comments before calling people sensitive. I've already acknowledged that I'm hypersensitive to shifting. But literally zero loaners from Chevrolet and  zero other vehicles that i've driven in my life have had similar behavior. 

 

Don't get me wrong. I love the truck, but I want it to work like it should and i'd be happy to keep the vehicle. This behaves worse than my 16' did when it took me 20k miles to have it diagnosed with a blown torque converter at 35k miles. I want this one to stop slamming myself and passengers uncomfortably in the vehicle. Currently, 4 times I have been slam shifted at under 2.4k miles,  (lurched forward, up-shift lag lurches you name it. ) which is unacceptable on any vehicle, not just a new one. 

 

I'd like to say that 3.5k miles is better now. but I can't. clunky and whammy even in sport mode, manual mode, trailer mode.  Even  after driving smooth at highway for 5-6 hours it turns sour when coming back to normal slow speeds in stoplight traffic. 

 

Again, if you have issues, please take it in to the shop, Maybe your reproduction of the issue can help us all. Maybe GM will acknowledge something to help us all.  That's all we all want. A truck we all bought to just work and not to be sensitive and slam us around. There are plenty of other ways to get slammed around and most of us prefer not to pay truck prices to get that thrill.