Vibration noise during low acceleration

[BainMan]

2021 Yukon XL Denali - vibration/rattle noise under light acceleration. Noise is loudest from passenger front. Noise occurs when accelerating with light throttle, and can be replicated in drive with foot on brake and rev lightly. In park, it's hard to get the noise to occur but has happened, again with a light rev. Heavy acceleration and the noise goes away.

The two videos don't quite do it justice, it's louder in person. I've tried to locate the noise, laying under the vehicle while the noise is happening, checking exhaust heat shields, the exhaust dampener, hand on transmission pan and oil pan, but I do not hear or feel the noise at all from under the Yukon. Noise can be barely heard from under the hood, all the way towards the back.

Also, the noise began after the dealership changed out the water pump.. Perhaps this is coincidence, I understand all the crazy 'ever sense you...' stories mechanics get.. However I'll add that I had to take it back twice after the water pump change, once because of the vibration noise noted above. I crawled underneath and found 3 missing bolts, 2 on the splash shield and one on the skid plate... The second time I had to take it back because they didn't fully tighten the coolant drain plug, and the first long drive caused it to leak and wear away the waxy coating on the frame under the drain plug... I tightened it by hand more than 1/2 turn. I asked for a different mechanic to check it but they claimed they are understaffed and it wasn't possible.. The 'mechanic' looked like he was 18 and fresh out of high school.. So my confidence in him doing the job right, or being able to diagnose is limited.. For what it's worth they wouldn't have touched it at all if not for the extended warranty..

Any ideas on how I can track this down or what it might be?

https://imgur.com/uh6g5Ox

https://imgur.com/xt4WNo6

 

[blanchard7684]

The buzzing noise sounds like something is loose and being excited by engine vibrations at just the right frequency.

I’d keep looking for something loose that would be “ in the path “ of a water pump job.

 

[BainMan]

Thanks, I’ve been trying but no luck yet…

 

[WalleyeMikeIII]

Maybe one of those missing bolts is laying on one of the shields underneath! Really unfortunate. But, you know how to make it happen, so take it back, and insist they resolve it.

 

[BainMan]

I always like to follow up with a conclusion for the next guy!

Dealership: Don't know, can't find it, wasn't us, not our problem.

Independent shop: Took less than an hour, we found the heater hoses weren't routed quite right sending a vibration into the firewall / heater core area. All fixed.

Worth what I paid at the indy. I won't be back to that GMC dealer..

 

[OR VietVet]

Did you approach the dealer with documented proof of what was found and done to fix the problem? You should. Was the initial water pump work warranty?

 

[BainMan]

I have not brought the proof back to the dealer, picked up the Yukon from the indy shop less than an hour before posting. Haven't even been home again yet. I hear what you're saying, but not sure its worth my breath at this point. I'll think about it some more though.

To add details, the dealer's service advisor is super nice and has apologized so many times about how they are short staffed with mechanics. The shop has at least 26 bays I counted, clean and organized looking shop, but only 2 actual mechanics (not counting lube/tire guys). The dude working on our Yukon looks like he is fresh out of high school. We asked for a different mechanic during the 2nd take-back, and he apologized again saying he just didn't have anybody else...

 

[OR VietVet]

I have not brought the proof back to the dealer, picked up the Yukon from the indy shop less than an hour before posting. Haven't even been home again yet. I hear what you're saying, but not sure its worth my breath at this point. I'll think about it some more though.

To add details, the dealer's service advisor is super nice and has apologized so many times about how they are short staffed with mechanics. The shop has at least 26 bays I counted, clean and organized looking shop, but only 2 actual mechanics (not counting lube/tire guys). The dude working on our Yukon looks like he is fresh out of high school. We asked for a different mechanic during the 2nd take-back, and he apologized again saying he just didn't have anybody else...

First: The tech shortage. For years techs were not paid what they were worth and so many have went out on their own. They have also went to the small mom and pop shops, like I always worked at, and get treated better and do not have to put up with dealership politics. Even at 72, I still get calls from shops to come back as a service manager or as a tech.

You did not answer my question as to whether it was warranty work or pay work. If you show them and tell them what happened, you may save a headache for another customer if the tech learns from their mistake.

Most techs, like myself, want to do a good job but dealership "flat rate" encourages short cuts and sloppy work practices.

 

[BainMan]

You did not answer my question as to whether it was warranty work or pay work. If you show them and tell them what happened, you may save a headache for another customer if the tech learns from their mistake.

Missed that part in my response. The water pump was 3rd party warranty. Dealership claimed they were impressed with the warranty company, it paid full shop rate and didn't bat an eye at the claim. It's an exclusionary policy, meaning everything is covered except items listed (like tires, battery, belts, fluids, etc...)