3.0L Duramax Mystery Rattle/Vibration?

Zane · March 3

Owners of 2023-2024 3.0L LZ0 trucks are reporting a persistent passenger-side buzz or vibration that occurs specifically under light load. While the noise often mimics an interior trim rattle, Service Bulletin PIT6300B identifies the actual culprit as a cracked catalytic converter brace or broken hold-down studs on the exhaust assembly. I’ve posted the full technical diagrams and the TSB details here for those who want to inspect their own hardware: https://www.gm-trucks.com/3-0l-duramax-lz0-passenger-side-rattle-exhaust-bracket-fix/

So this has me curious:

How many of you are currently hearing this vibration during light acceleration?
For those who have gone to the dealer with this or a similar problem, how did they address?
Has anyone found the bracket cracked and/or missing/broken studs?

Z45 · March 4

2024 LZ0 built July 2024 - Nothing observed (VIN = 3)

Edited March 4 by Z45

redwngr · March 7

My 40,000 miles '23 LZO has no rattles.

jeffgee · March 12

2023 Z71 1500 3.0 duramax vibration started at 91,000 +- took it into the dealer 12-3-25

and they changed a Worn exhaust hanger support bracket? i had not found this article yet. vibration is in any gear rpm 1500 to 1700 - really noticable on up hill slope and when engine is cold at start. new exhaust hanger / support bracket did nothing - may have made it louder. I haven't gone in again because its out or warranty and exhaust bracket was $900.00+ . now at 102000 miles - still have the vibration - looked under the vehicle once - the engine bay is so crowded - hard to even get a hand in there to feel around .

GriffinM · March 27

2023 GMC Sierra 1500 3.0L duramax LZ0

Bought this truck used at 75k km. Noticed vibration right away. Found a broken stud between the block and converter bracket on my own.

GMC customer service told me that it was covered under powertrain warranty, so I brought it to the dealership. Paid $200 diag fee for them to tell me what I already knew and it's not covered under warranty.

After further inspection it turns out the converter bracket is broken around the upper stud, and the lower stud is broke off in the block. Vibration between 1500-1700rpm and worse when going up hill or towing. Very annoying. I've read online that people have has this fixed under powertrain warranty, but GMC is saying they won't help.