Hard down shift while coming to a complete stop - Page 3 - Chevy and GMC Duramax Diesel Forum
11-16 LML Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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post #21 of 34 (permalink) Old 08-08-2017, 02:20 PM
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I am experiencing the same thing in my 2016. It happened a couple months ago in the rain- rear tires chirped. Happened again yesterday several times. Did not notice if the truck was in Regen mode (wish it would indicate on the instrument cluster). Anyone have any success taking it to the dealer for a repair?
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post #22 of 34 (permalink) Old 08-08-2017, 04:21 PM
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What did GM customer support do for you?


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post #23 of 34 (permalink) Old 03-17-2018, 11:13 AM
 
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Not to restart an old thread but... I'm having this same issue with my truck (2016 GMC 2500HD with 29000Km's) where coming to a stop it actually feels like I'm being re-ended. And at some point like it wants to stall, I don't think I'm due for a regen yet, I have had the pressure manifold switch changed about 2 months ago under warranty but it has never been this bad..... I had asked for a relearn on it after the switch was changed and the dealer said I didn't need it.... where do I go from here??
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post #24 of 34 (permalink) Old 03-18-2018, 02:17 PM
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Originally Posted by Tigger72 View Post
Not to restart an old thread but... I'm having this same issue with my truck (2016 GMC 2500HD with 29000Km's) where coming to a stop it actually feels like I'm being re-ended. And at some point like it wants to stall, I don't think I'm due for a regen yet, I have had the pressure manifold switch changed about 2 months ago under warranty but it has never been this bad..... I had asked for a relearn on it after the switch was changed and the dealer said I didn't need it.... where do I go from here??
How are you determining you're not due for a regen? Unless its happening every time you stop, I'd bet its the known bump during regen while stopping.

2015.5 Chevy Duramax 2500HD
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post #25 of 34 (permalink) Old 03-18-2018, 02:48 PM
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Here is a perfect example of where a tune could fix a problem. If the transmission down shifted sooner while the engine was in regen it would match the new idle rpm to the transmission rpm better and eliminate the bump. Or it could disable the rpm increase on decel. Or it could soften the shift on decel when regenerating. Or it could soften the shift on decel all of the time. Or ?????

But now the gummament is preventing us from improving our vehicles, even though it makes no difference to anything they care about.
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post #26 of 34 (permalink) Old 03-18-2018, 06:37 PM
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Mine always shifted the same in regen or not.

Only similar 'bump' mine ever had was the one that is commonly associated with fuel slosh.

And that only occurred with a certain combination of decel rate and fuel volume in tank.


Downshifting hard enough to 'chirp' the tires makes me there is a physical problem with the transmission.
If not, there would have been many many complaints posted about the 'chirp' between late 2010 and now.

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post #27 of 34 (permalink) Old 03-19-2018, 11:45 AM
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This whole thread is based on complaints. I could recreate the situation in my '15 dmax while in regen when downshifting from 2-1 at a light or stop sign. The engine would want to stay in elevated idle and that would cause a lurch when shifting from 2-1. Only time it ever happened. I'm not saying folks haven't experienced fuel slosh, but what I and what I believe a bunch of others experienced on here is FAR from that.

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post #28 of 34 (permalink) Old 03-19-2018, 05:45 PM
 
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How are you determining you're not due for a regen? Unless its happening every time you stop, I'd bet its the known bump during regen while stopping.
I ball park it as I don't know any other way...I thought I was just through one recently.....BUT..... apparently not.... it was the regen... or I am assuming it was but it was worse then normal.... (heres the kicker ) ...... I think it was worse then usual as I had just filled up and the regen along with the fuel slosh was combo I have not had before.....now is my truck the only one that does the regen and starts to smell like something is burning ???? I know with the regen it heats it up quite a bit ( Or so I was told ) and I didn't notice it the other day as I normally smell it when I park in the garage that day I was outside in the wind...
Thanks guys!!! I guess I jumped the gun!!!
Is there a way to know when its regen is going to happen??? There must be something ......
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post #29 of 34 (permalink) Old 03-20-2018, 09:51 AM
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hard to tell when a regen is going to start without a cts2 or something to tell you your soot gram count

2012 GMC Sierra 2500HD Diesel 2wd Crew Cab. Stock. 200 mile regen club
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post #30 of 34 (permalink) Old 09-05-2019, 06:02 PM
 
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^6 speed allison

Help Help Help !!! I have a 2019 chevy high country I bought New May 21 2019 going to work in the mornings I notice that when I come to a stop the down shift is so hard it jerks me forward this happens intermitinly and only when I slow downI know have 11,500 miles it seems to be worse the purpose of a good transmission is to make the shifting smoother Ive been getting the nothing wrong with it attitude from the dealer 70,000.00 whats up.
.
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