Jump to content

6 Speed Transmission Clunk Downshift

JacobC1983
 Share

Recommended Posts

g2full Enthusiast

g2full

Posted
Posted
On 3/24/2018 at 7:48 PM, Hooper_c4 said:

It's a Chevy thing. They all do it

Sent from my SM-G930V using Tapatalk
 

Truth in this statement. The '04 I just got rid of did it for the entire 4 years I had it. Never caused issues.

  • Haha 1
  • Replies 70
  • Created
  • Last Reply

Top Posters In This Topic

Popular Days

Top Posters In This Topic

Popular Days

Popular Posts

Grumpy Bear
Grumpy Bear

I'll be sure to tell my truck's 6L80E transmission about this. It has been picture perfect for nearly 60,000 miles. Evidently it doesn't know that it spoiling the others awful reputation.  

Mike GMC
Mike GMC

I believe the "mine is fine" posts are in response to the equally useless, "they all suck" posts.   That said, have you done a fluid change?  What does the fluid look like?  How is the fluid

Grumpy Bear
Grumpy Bear

Problems with threads like this. 10 guys who never met each other with 10 different situations assuming 10 different assumptions are creating the exact same issue. Make a guys head hurt....  

Posted Images

rudyb Enthusiast

rudyb

Posted
Posted (edited)

My '16 has an aweful downshift while coasting down from 32mph->28mph. The seat belt has caught me a few times. It's pretty aggresive. If I'm braking it doesn't usually happen, just when I see a red light and let off the gas pedal. I also have some strange stuff while accelerating, but it's difficult to replicate. Sometimes it will accelerate through the gears like a dream. Other times the truck seems to be drunk and can't figure out what gear it's supposed to go to. 

Edited by rudyb
njk4o5 Enthusiast

njk4o5

Posted
Posted
15 hours ago, rudyb said:

My '16 has an aweful downshift while coasting down from 32mph->28mph. The seat belt has caught me a few times. It's pretty aggresive. If I'm braking it doesn't usually happen, just when I see a red light and let off the gas pedal. I also have some strange stuff while accelerating, but it's difficult to replicate. Sometimes it will accelerate through the gears like a dream. Other times the truck seems to be drunk and can't figure out what gear it's supposed to go to. 

classic k2xx transmission tuning

Sierra Dan Senior Enthusiast

Sierra Dan

Posted
Posted
16 hours ago, rudyb said:

My '16 has an aweful downshift while coasting down from 32mph->28mph. The seat belt has caught me a few times. It's pretty aggresive. If I'm braking it doesn't usually happen, just when I see a red light and let off the gas pedal. I also have some strange stuff while accelerating, but it's difficult to replicate. Sometimes it will accelerate through the gears like a dream. Other times the truck seems to be drunk and can't figure out what gear it's supposed to go to. 

Throw it in M5, and a run a few tanks of E85 through the system if you are E85 capable.

g2full Enthusiast

g2full

Posted
Posted (edited)
On 3/24/2018 at 7:48 PM, Hooper_c4 said:

It's a Chevy thing. They all do it

Sent from my SM-G930V using Tapatalk
 

My 04 did it for sure. lol. I'm so used to it I don't even notice anymore really. But I'd love for it to work as designed.

Edited by g2full
  • 1 month later...
Tigstoy97 New Member

Tigstoy97

Posted
Posted (edited)

My 17, k1500 is having same issue, started at 38K. Multiple trips to dealer (multiple re-flashes / updates), even opened a case with GM on it. Duplicated at the dealer, got ever excuse other than a possible fix in the works. just waiting for the 60K to expire, so my aftermarket extended warranty can deal with it. Got worse towing - had a up shift shudder from 30-45mph - with only a 4k load behind it, very disappointing.

 

Glad I did not trade in my 04 Suburban, 4 gears seems to be less problems than 6.

Edited by Tigstoy97
  • 3 weeks later...
6.2_GMC_DEN Enthusiast

6.2_GMC_DEN

Posted
Posted

It took hours any many revisions to fix the driveline clunk issue I experienced. It is a combination of upshift and downshift scheduling problems, torque converter lock up and unlock at the wrong times,  desired output torque factor issues, torque adder issues, stall torque management, tip-in torque management, limit torque management, torque reduction, and more. Basically the stock tune is commanding too much of everything at the wrong times.

 

Mine shifts like butter at part throttle and is nice and crisp at WOT. The way it should of been from the factory.

 

Slide1.JPG

Slide2.JPG

Slide3.JPG

Slide4.JPG

Slide5.JPG

  • Thanks 1
wtfandy Enthusiast

wtfandy

Posted
Posted (edited)

I didn't have an issue with my 2017 1500, but got some of the symptoms mentioned in this thread. Set an appointment for Tuesday to drop off. Wondering if I can take this to work Monday.

 

2018 Sierra 1500 CCSB with 7.5k miles

 

http://imgur.com/gallery/DuennvB

Edited by wtfandy
  • 2 weeks later...
Lamekurt Enthusiast

Lamekurt

Posted
Posted
On 2019-01-11 at 9:53 PM, thekevin said:

My 2018 will clunk in the same spot pretty much every day. On the 4 lane to my house there is about a half mile down hill coast, then a mile long uphill and right at the top is my exit that is also uphill that comes to a stop sign. Pretty much every day when slowing for the stop sign it clunks really hard on the 2 - 1 shift. I have a Range AFM disabler.


Sent from my iPhone using Tapatalk

Ever find a fix for this? My 18 has the same thing too 

CSI-WALLEYE Enthusiast

CSI-WALLEYE

Posted
Posted

How common is this problem?  are the problematic transmissions defective or is this a design flaw?  If it is a design flaw why don't they all have problems?

Rusty Shackleford Enthusiast

Rusty Shackleford

Posted
Posted

Had this issue when I got my 2018 w/6spd. Talked to the trans guy at my dealer and he told me to run it in tow/haul every time I drove it for about two weeks, then revert back to normal. It largely solved the problem. I get a hard downshift about once a week now, much better than it being a daily occurrence. 

  • 5 weeks later...
Vonpaco New Member

Vonpaco

Posted
Posted

I am new to this site and found it while researching the harsh down shift issue. I purchased a new 2018 1500 with the 5.3 and 6 speed in july of 2018. Have had it into the dealer 6 times for the harsh down shift on rapid deceleration. The problem began after it hit around 2k miles and was ignored until about 17k miles. They performed the normal relearn repairs and sent me on my way. They finally agreed there was an an issue when i didn't go away and found the 3-5 reverse housing was leaking. They repaired ( only 1k miles on repaired trans) the trans and corrected the problem. Unfortunately, they created another issue I am now dealing with. The truck now slams out of overdrive when I push the throttle to pass another car. The dealer is of course saying it needs to "learn" the shift points again and want me to drive it another 1k miles.

I have my 7th service appointment on Wednesday. I attached my service invoice to show what they did. 20190513_210240.thumb.jpg.39d2ebb94f419167505debc459fd5907.jpg

  • 2 months later...
2014RedRado New Member

2014RedRado

Posted
Posted

My 2014 silverado does this when i'm in reverse and switch it in drive without stopping completely. Also happens when my truck try's downshift from 3rd to 2nd gear while i put torque on it. I haven't heard of a way to fix it. seems pretty common 

Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
On 4/13/2019 at 7:29 AM, CSI-WALLEYE said:

How common is this problem?  are the problematic transmissions defective or is this a design flaw?  If it is a design flaw why don't they all have problems?

Problems with threads like this. 10 guys who never met each other with 10 different situations assuming 10 different assumptions are creating the exact same issue. Make a guys head hurt....

 

How would one begin to sort that actual defective units for those whose operators are aggravating a normal situation like the one below: 

 

25 minutes ago, 2014RedRado said:

My 2014 silverado does this when i'm in reverse and switch it in drive without stopping completely. Also happens when my truck try's downshift from 3rd to 2nd gear while i put torque on it. I haven't heard of a way to fix it. seems pretty common 

What? You mean you can't abuse a transmission and have it ACT NORMALLY?  :banghead:

 

:crackup:

  • Like 1
  • Haha 1

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.

  • Forum Statistics

    250.5k
    Total Topics
    2.7m
    Total Posts

  • Member Statistics

    342,964
    Total Members
    8,960
    Most Online
    BrandonFranceschi
    Newest Member
    BrandonFranceschi
    Joined

  • Who's Online   4 Members, 1 Anonymous, 1,533 Guests (See full list)

  • Latest Articles

  • Posts

    • Jsdirt
      2010 Avalanche 5.3 not running correctly after engine swap.

      By Jsdirt · Posted

      If everything checks out at the MAF, then the MAF is BAD, new or not.   You don't need a signal generator to troubleshoot this. PCM needs ALL powers and ALL grounds able to light a halogen headlight bulb - if it can light the bulb bright, then the wiring is good enough to run the PCM.   Best thing you can do for yourself is spend some time here: scannerdanner.com - Check out all his YouTube videos on similar issues. If you decide to subscribe it's the best bang-for-buck ratio in the automotive world, hands-down. He's got TONS of free vids on YouTube, too.
    • Tyler Gibbs
      PF63 Oil Filters Going Away?

      By Tyler Gibbs · Posted

      You got that Hengst D110??
    • contrabombarde
      2010 Avalanche 5.3 not running correctly after engine swap.

      By contrabombarde · Posted

      Yes, I used my multimeter to probe all of the wires at the MAF, both with the sensor connected, sensor disconnected, key on engine off, key on engine running, etc etc etc. I probed all of the wires again at the PCM, at the connectors, etc. All voltages are what they should be according to the service manual/wiring diagrams. All grounds are good, less than 20 millivolts from the battery negative under load. Both at the connector of the MAF, at the PCM connector etc.      I know this throws a pretty big wrench into things, but this truck was acting up before the swap. I don't have very much information, if any on what was causing it, but if you cleared all of the dtcs it would do the same thing where it would crank, fire, then die. And it would do the same thing a dozen or so times, and eventually it would start and run, but the difference is that it would run and actually be drivable. Whereas now if you can drive it at all, it goes into reduced power mode almost immediately, and even then it's not running correctly. When you come to a stop at a light it stumbles down to for 500 RPM before catching itself and returning to the smooth idle. And if you go more than about 50% throttle then it immediately goes back to doing the misfire thing.    Like I said, I know that throws a wrench into things, and unfortunately I was not able to pull any data or anything like that before I did this work, so I don't have much to go on.    I'm trying to not fixate on one particular thing as the cause of the problem, but it seems like all avenues are pointing me towards the PCM. Like I said I have tested the wiring extensively (see above), and during cranking the sensor does produce seemingly legitimate values at least according to my multimeter, but as soon as the engine fires those values quickly descend into gibberish. I've tried it with multiple different known working sensors, I have done literally every test I can think of multiple times on the wiring (probing the signals, probing the pins with the sensors unplugged, probing the pins at the PCM, voltage drop, voltage drop under load, continuity, ohms, and double-checking everything against the wiring diagrams/ proper values in the service data.)    Another thing that pushes me towards a possible PCM failure is, I have noticed in troubleshooting a little bit taking a break and coming back, that when I leave the truck to sit for a while and cool off, it starts and runs smoothly when I first start it up. However once it warms up. It starts having problems. For example, when I went out to the truck this morning after it had been sitting overnight, I was actually able to drive it down the block. And then once I got on the throttle a Little bit after going about a thousand ft, it started misfiring again. I pulled it back into the driveway, shut it down, and started it back up. It idled smoothly. As soon as I touched the throttle it did the misfire thing again. From then on as soon as I started it it would misfire. I shut the truck off and went to go get a coffee and do a bit more research. When I came back out I started the truck up and it immediately went into the smooth idle. After a couple of minutes of playing around with it, it would not idle smoothly anymore. Let it sit a couple of hours, rinse and repeat. This makes me think with temperature change something is going wrong inside the PCM. I have the PCM out of the 2007 donor vehicle and I'm thinking of getting a one-day subscription to the ACDelco programming service to try and program that and see if it helps.   Like I said, I'm really trying to not fixate myself on one potential cause, but it seems everything is pointing me towards PCM failure. I would really like to try to confirm that, but unfortunately I don't have an oscilloscope or a signal generator to do the GM service procedure where you feed 5 khz into the signal pin. 
    • Jsdirt
      2010 Avalanche 5.3 not running correctly after engine swap.

      By Jsdirt · Posted

      Ahh, sorry about that - I got some bad info. Newdude is correct. That's what I get for working 13 hours straight ... on my "vacation", lol.   Should've checked the files I had instead of the internet.   Anyway ... this is GREAT news, since this would've been an absolute friggin nightmare to get working.   I don't think the lack of VVT is causing this - you've got another issue. Wiring, I'm betting.   I'm telling you right now, your computer isn't bad. If it worked before the swap, it's working now. You need to do some more (better) diagnostics and figure out exactly what you're missing. Did you test every wire directly at the MAF? Have 5V reference? Ground? If you're reading ZERO g/s, your Hz isn't much use - it's going to be the wrong value anyway. The MAF is not working, and you need to find out WHY.   I got this off the net, so VERIFY first: Pin A: Black (BLK) wire, Circuit 552, serves as the Sensor Return (Ground).  Pin B: Tan (TAN) wire, Circuit 472, carries the Intake Air Temperature (IAT) signal.  Pin C: Yellow (YEL) wire, Circuit 492, is the primary MAF Sensor Signal output to the PCM. Pin D: Pink (PNK) wire, Circuit 339 or 539, provides Ignition 1 Voltage (Power).  Pin E: Tan/Black wire, Circuit 552 or similar, often associated with the Intake Air Temperature ground or signal return.  Global-A list: https://postimg.cc/KKJnQC85    
    • parthery
      GM Hard Folding Tonneau by REV review

      By parthery · Posted

      Correct....the end user can't reach to Realtruck directly like they can if they purchase a Bak, Undercover, etc...  It has to go through a dealer.

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...