Loud clunk at deceleration

[aha1987]

Has anyone else heard a loud clunk ( occasionally) when decelerating? It happens right before I come to a complete stop. I believe it happens when the transmission goes into first gear

[aha1987]

Here is a video of the noise 

ADDB3EFA-A4D9-4F75-891A-66E35F29428F.MOV

[JimCost2014]

45 minutes ago, Aycock1987 said:

Has anyone else heard a loud clunk ( occasionally) when decelerating? It happens right before I come to a complete stop. I believe it happens when the transmission goes into first gear

Would guess the number of people that have heard their transmission "clunking" would be in the thousands. 

[aha1987]

24 minutes ago, JimCost2014 said:

Would guess the number of people that have heard their transmission "clunking" would be in the thousands. 

It has never done this until this week. I have about 4K miles on It

[JacobC1983]

I also have a loud popping or clicking noise when the truck goes into first gear right before a stoplight.  It doesn't do it all the time, but it has happened about once a week for a while now.  Truck is at 6000 miles.  I can hear it very well when I drive in the neighborhood with the windows down.

[Sierra Dan]

8 or 10 speed ?

[JacobC1983]

10 speed

[aha1987]

Mine is a 10 speed

[Mike Shap]

Can the loud clunking sound be fixed?  Has anyone had their truck repaired for this problem?

[Casey Nelson]

Hello everyone, I’ve got a 2020 At4 1500 6.2 with the same clunk when slowing down. Any updates with this?

[especter]

I just had this happen to me. This is after I towed a 4300 lb vehicle on a u-haul auto transport for about 120 miles. I dropped off the trailer, drove home, and  it happened to me while decelerating to a stop; shift from 2 to 1 gear. I was able to reproduce it several times after that. I scheduled a service appointment to see a master tech. Any idea what is causing it?

[bshort]

1 hour ago, especter said:

I just had this happen to me. This is after I towed a 4300 lb vehicle on a u-haul auto transport for about 120 miles. I dropped off the trailer, drove home, and  it happened to me while decelerating to a stop; shift from 2 to 1 gear. I was able to reproduce it several times after that. I scheduled a service appointment to see a master tech. Any idea what is causing it?

Going to be told "operating as designed."  

[especter]

I just had the dealership perform the transmission service on my 2019 Sierra 1500 5.3L 8-speed. Service was performed on Tuesday. 

 

Parts included: BG 6600 Transmission Flush kit ($47, includes 106BG & 310BG), Filter (GM Part No. 24274402), and Fluid (GM Part No. 88865601)

 

Issues thus far:

 

Last night I noticed an oil spot in my driveway, put some cardboard under the transmission pan, and drove it to the dealership this morning. They confirmed the pan was "seeping" and blamed it on a defective gasket. 

 

Looking at the parts list, they used the AC delco ATF. Should they be using the Mobile 1 Synthetic LV fluid per the 18-NA-355 bulletin??

 

Any help would be appreciated, because I'm about to blow my gasket..........

@bshort

[bshort]

17 hours ago, especter said:

 

 

Any help would be appreciated, because I'm about to blow my gasket..........

@bshort

You already did...on the transmission.    One of the reasons that I try to avoid the dealer at all costs....they tend to be somewhat clueless and always seem to F something up.  Sometimes you have to write things out in crayon for the service writer.  Have them use the correct ATF when they change that pan gasket out.  

[especter]

2 hours ago, bshort said:

You already did...on the transmission.    One of the reasons that I try to avoid the dealer at all costs....they tend to be somewhat clueless and always seem to F something up.  Sometimes you have to write things out in crayon for the service writer.  Have them use the correct ATF when they change that pan gasket out.  

Oh man, the service writer is completely clueless. I printed, highlight, and showed him all of the relevant GM service bulletins & he completely disregarded them. One bulletin identified that GM does NOT recommend aftermarket additives and fluid flushes for normal service. The other being the procedure for the fluid exchange procedure using the ATF machine w/ 20 quarts of the Mobile Synthetic ATF HP fluid. 

 

Eventually, after not being able to deal with me any longer he called over the shop foreman  & we had an in depth conversation about the 8 speed transmission bulletins. FINALLY, they agreed to use the Mobile 1 Synthetic ATF HP fluid (blue label). 

 

Fingers crossed for smooth operation and no leaks when I pick up the truck later today........

MC-10159572-9999.pdf

MC-10163241-9999.pdf