Clunk noise at acceleration until warms up

[Chinzo]

My 2015i Denali had audible noise coming from rear upon acceleration, anyone else experiencing this? When vehicle is cold, upon acceleration there is single clunk or click noise, and no noise while driving until next stop then acceleration, after about 15-30min driving it goes away. I just found this to be annoying now. Dealer wants to open rear and needs vehicle whole day.

 

[motorwerks]

There's nothing they can do short of replacing your entire transmission assembly. Yes, that's what it is. Early 8-speed had increased clearances in the clutch packs which click when cold. After February 2015, all of the early 8-speeds were purged from the GM plants in favor of more updated 8-speeds with tighter tolerances.

 

[Chinzo]

There's nothing they can do short of replacing your entire transmission assembly. Yes, that's what it is. Early 8-speed had increased clearances in the clutch packs which click when cold. After February 2015, all of the early 8-speeds were purged from the GM plants in favor of more updated 8-speeds with tighter tolerances.

Just contacted our local dealer with this new-found knowledge thanks to you, and they've contacted GM's TAC line, they were advised to do "Pressure Test" and if necessary they said they will replace the transmission, hate to see brand new car being monkey-d with. Appointment for test is next week and will update back once find more info on it.

If anyone knows what this Pressure Test is all about let me know! thanks

---------- Post added at 01:07 PM ---------- Previous post was at 01:04 PM ----------

Oh yes, i know how to google, so i'm not asking about pressure test in transmission in general terms, so please don't copy paste too much info that you've found from other sites. I'm asking more specifically on 2015 Yukon Denali and its new-old 8 speed transmission, relating to clunk noise and how pressure test will fail etc., and need real advise from someone who got this done or have experience.

 

[Chinzo]

Just got the vehicle back from the dealer, they've installed brand new 8 speed transmission and it is not making that noise anymore. Dealer explains that tolerance in transmission is off and harmonics noise making it sound like its coming from the rear. 2 day job at the dealer, and besides already expected grease spots from mechanics hand and clothes on certain area of the vehicle, all went well and i'm pretty happy about it.

Next fix would be bottom portion of the heated seat on drivers side quit working...

 

[johnnybogey]

Thanks for info. I have been experiencing the same issue. The dealer drive it around and concluded nothing wrong. They even provided me with an information sheet trying to explain that this type of noise is normal and common.

Will go back to dealer with this new information and report back.

 

[paulb55]

This is supper helpful...we are having the same issue.
Thanks. Will take this in.

 

[Chinzo]

UPDATE:

So far about 3,000 miles on new transmission and everything appears to be well.

 

[johnnybogey]

Can't tell you how frustrating this process is. I have now dropped off my yukon twice with the dealer and they explained that the noise is "normal" operating condition. TBH, I don't even know if they were able to replicate the noise.

Not sure what else I can do except find another dealer (which is tough given that aren't many around by me).

I explained to them that I read on the GMC dedicated forums that a "pressure test" should be performed but the dealer sounded irritated and said that they can't go by what forums say.

Any suggestions?

 

[ezdaar]

go to another dealer and tell them that XXXX dealer is being a **** about fixing a known issue.

 

[paulb55]

Make sure they test your truck when the trans is cold. if its not, they will not hear it