6 Speed Transmission Clunk Downshift

[g2full]

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

It's a Chevy thing. They all do it

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

[rudyb]

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 January 24, 2019 by rudyb

[njk4o5]

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]

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]

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

It's a Chevy thing. They all do it

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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 January 24, 2019 by g2full

[Tigstoy97]

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 March 12, 2019 by Tigstoy97

[6.2_GMC_DEN]

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.

 

[wtfandy]

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 March 31, 2019 by wtfandy

[Lamekurt]

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.


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

[CSI-WALLEYE]

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]

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. 

[CSI-WALLEYE]

should you use towing mode every time you tow or only when towing heavy items?

[Vonpaco]

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. 

[2014RedRado]

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]

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?