6 Speed Transmission Clunk Downshift

JacobC1983 · March 24, 2018

Has anybody with clunky downshifting on their 6 speeds switched out their transmission fluid to another’s brand/type of fluid other than factory with any help with the downshift clunk?

SWOYER · March 24, 2018

In for clues. Tune helped. I saw online greasing the spline on the transfer case.

JacobC1983 · March 24, 2018

Tune from Blackbear didn’t help me, just changed when and how the downshift clunk happened.

Edited March 24, 2018 by JacobC1983

johnboy105 · March 24, 2018

I have this all the time.... I had taken it in to my dealer and there was a software update for the trans, which they applied - it seems to help a 'bit' at first (definitely not a complete fix), but after a bit of time (oh say a few weeks), I couldn't really tell any update had been done.

My "fix" would seem likely a bit extreme by most here, but I've just traded for a 2018 LTZ Z71 (that has the 8-speed by default) and with a test drive, I found a HUGE improvement in the trans response on that 8-speed. I know the 8-speeds of 2014 through 2016 or so had plenty of problems, but the 2018 LTZ Z71 I drove was surprisingly perfect.

JacobC1983 · March 24, 2018

lol. yea trading out to a different truck would probably fix the problem. Was hoping to find something more pocket book friendly until the 2019s arrive with the 10 speeds. The 10 speeds I have test driven have been wonderful in the 2018 yukon denali and escalades.

I have had mine in the dealer and have the latest software also.. and reproduced the clunk and got the "its normal" talk.

Edited March 24, 2018 by JacobC1983

Donstar · March 24, 2018

I would stick to seeking a dealer repair rather than fixing myself. If you can easily replicate the problem while driving normally then maybe ask the dealer if you can test drive a similar vehicle to confirm the clunk is normal. I can sometimes get a clunk when I'm backing out of my driveway and putting it into D and stepping on the gas while still rolling backwards. It won't clunk if I stop the vehicle prior to switching gears. My wife's Toyota under the same conditions will hesitate but not clunk. I will report that it clunks before my warranty expires to see if anything abnormal is causing this particular clunk.

Nanotech Environmental · March 24, 2018

Mine will occasionally give a very firm downshift at slower speeds, usually when I'm hard on the brakes. Not sure if that's the same as the clunk that the OP is referring to.

It only does it once in a while on my truck. At first it alarmed me a bit, as it does seem to hit pretty hard sometimes when it happens. Now, I don't really notice it that much & it doesn't seem to harm anything & I've (probably) semi-unconciously modified my driving style a bit to accomodate it.

There have been a few small quirks like this that I've noticed on this truck compared to my previous 2006 Sierra. At first they caught me off guard, then I got used to them, as I slightly adjusted how I drove the truck. They don't really cause notice much anymore.

Given how much better this truck is than my past 2006 Sierra, I don't mind making small driving style adjustments. I'd much rather have this truck with a few small quirks, than the old truck.

MrElussive · March 24, 2018

I feel it only sometimes on an uphill when the transmission downshifts to third gear. I believe it's when the torque converter is locked up for fuel economy and the transmission makes the downshift to third while the torque converter is still locked, so it does not happen often. Otherwise I find the 6-speed transmission on this truck to be a very smooth shifter, actually. I don't think changing transmission fluid will make any difference.

Hooper_c4 · March 24, 2018

It's a Chevy thing. They all do it

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Hooper_c4 · March 24, 2018

It's a Chevy thing. They all do it

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Especially when cold! Clunky and jerky things! Starting to dislike mine the more I own it!

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adamj2121 · March 25, 2018

My 2016 with the 6 speed is the worst shifting vehicle I have ever driven. Most shifts are clunky and there are several major hesitations everyday that make the truck suck to drive. I’ve considered a Black Bear tune, I’m just afraid I won’t see any improvement with it. The dealer currently has my truck to look at the shifting issues and I have a 18 Sierra with the 8 speed as a loaner, much smoother shifting and more responsive than the 6 speed. I haven’t noticed any of the issues I have seen reported on here for trucks with the 8 speed.

Grumpy Bear · March 25, 2018

19 hours ago, Hooper_c4 said:

It's a Chevy thing. They all do it

2 hours ago, adamj2121 said:

My 2016 with the 6 speed is the worst shifting vehicle I have ever driven.

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.

WC_LTZ · March 25, 2018

My 2016 with the 6 speed is the worst shifting vehicle I have ever driven. Most shifts are clunky and there are several major hesitations everyday that make the truck suck to drive. I’ve considered a Black Bear tune, I’m just afraid I won’t see any improvement with it. The dealer currently has my truck to look at the shifting issues and I have a 18 Sierra with the 8 speed as a loaner, much smoother shifting and more responsive than the 6 speed. I haven’t noticed any of the issues I have seen reported on here for trucks with the 8 speed.

I’m in the same boat. About to take mine to dealer to look at. Shifting is terrible to the point it is sometime dangerous to drive.

Mike GMC · March 25, 2018

I guess mine is a weird 6 speed as well. It shifts very well, no clunking or hesitation. The torque management is evident in the 1-2 shift at full throttle, but that's not the transmissions fault and easily tuned out.

2017_whitez71 · March 25, 2018

22 hours ago, Hooper_c4 said:

It's a Chevy thing. They all do it

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Wouldn't say it's a Chevy thing. I've had 2 different k2's with 6 speeds and both have been flawless. Have never had any weird shifting, even when cold. My dad also has a 6 speed and he hasn't had any problems with his. My brother has an 6.2 with an 8 speed, he has had issues with harsh downshifting.