Transmission 'thump' - stopped but in drive , idle

[curte]

2015 Tahoe LTZ, 99500 miles, 5.3L.

Recently, have had a few occurrences of strange noise after coming to a stop but still in drive (e.g., stoplight, in a drive through lane) the drive train makes a 'ker-chunk' thump. It's only happened a couple of times, once for the wife, couple of times for me now. Twice, very 'soft', noticeable but about a "did I really hear that?" level. One time, while in a drive thru lane, it happened, hard enough I thought guy behind me bumped me. Hard enough that I got out of the vehicle to check for damage, thinking I was bumped. That's when wife said it had happened for her before once. All this over that last couple of weeks, but haven't been driving it much lately, short trips on local surface streets and freeways.

Looked through this forum for something similar, but didn't find anything.

No previous drive train problems, bought it used at 31K.

I'm way past due for transmission and transfer case fluid changes, now scheduled at the dealer for Monday. Anything else I should look for / tell the service advisor?

Thanks

 

[ivin74]

Have you ever service your transmision?

Sounds like the valve body solenoids are dirty and may need to be changed out. The newer trannys are not like the old ones were they could go for ever. The newer transmision have more clutches and more clutches means more clutch dust on the oil and that my friend clugs up the solenoids

 

[Doubeleive]

could be something with the torque converter not disengaging properly, you can mention to the service advisor and have them note it on the service request but I wouldn't hold my breath as to if they bother with it or not unless it is doing it on a test drive or something. maybe google and see if there is a tsb on it.

 

[curte]

Thanks for these replies.

I did searches for similar problems but searches for variations of "transmission" "noises" turns up a lot of fodder to sift through.

No previous transmission service. (Yes, I missed a fluids change at 45k miles. I was told fluids were changed as dealer prep when I bought it at 31k.)

Had another 'soft' occurrence yesterday while slowing down rolling at idle toward a stoplight. However, nothing else during that trip, several other stoplights on surface streets and a few highway miles.

I intend to mention these occurrences to the SA, see what he says regarding possible causes. Thanks for the tips regarding torque converter not disengaging and the valve body solenoids.


Thanks
2015 Tahoe LTZ, 99500 miles, 5.3L.

 

[Fifty]

It’s the factory tune of the transmission and no way to get rid of it other than having the TCM rep programmed.

the computer holds 3rd gear when slowing to a stop (for epa reasons believe it or not) and won’t shift to first until the vehicle stops.

but sometimes the vss in the trans sends the signal that you are stopped and it shifts to first but you are still rolling a bit. it’s a rough shift when this happens.

usually it’s reported as a “surge” forward as well as a clunk.

 

[curte]

No surge that I've noticed, but then I've had my foot on the brake at the time, e.g. at stoplights. I suppose the one time I thought I was 'bumped', that might have been like a slight surge forward.

Sent from my SM-N960U1 using Tapatalk

 

[curte]

Odd that we've only noticed it recently, if that's "normal" per the programming, but maybe the fluid change will reduce/eliminate the noticibleness of it occurring.

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[curte]

results - told the service advisor about the occurrences and the suggested causes discussed here. Tech inspected and found transmission "fluid very dark and worn". Able to recreate problem one time at a stop light. Inspection found all drive line components ok, no codes found. After ATF fluid change, no more clunks during test drive. "Suspect ATF fluid change eliminated the issue due to condition of the fluid.".

Also did the fluids for transfer case, brake system, front and rear differentials.

As Doubeleive suggested, I didn't hold my breath, but the story and suggestions at least got before and after test drives and the tech experienced the problem.

Thanks again for the comments.

 

[stapleto]

Did you check the driver side motor mount?

 

[Fless]

results - told the service advisor about the occurrences and the suggested causes discussed here. Tech inspected and found transmission "fluid very dark and worn". Able to recreate problem one time at a stop light. Inspection found all drive line components ok, no codes found. After ATF fluid change, no more clunks during test drive. "Suspect ATF fluid change eliminated the issue due to condition of the fluid.".

Also did the fluids for transfer case, brake system, front and rear differentials.

As Doubeleive suggested, I didn't hold my breath, but the story and suggestions at least got before and after test drives and the tech experienced the problem.

Thanks again for the comments.

Think about adding the word "Solved" to the thread title. That will help future searchers.