pinging, popping, grinding sound from rear in v4 mode

[bobbyd]

Hi all -

I've had my new 2014 GMC Sierra SLT all-terrain for a few weeks now, up to just about 800 miles.

About a week in, I noticed a strange pinging/popping sound from the rear. I can only hear it at relatively slow speeds, and I'm unable to determine which side it's coming from, or if it's dead-center. I have discerned, by monitoring the info screen in the dash, that it only seems to happen in v4 mode; and seems especially prone to occur when switching between v4 and v8 mode, regardless of whether it's going from v4->v8 or v8->v4. The ride, itself, does not appear to be affected; it's just the very wrong-sounding noise that causes concern.

I'm going to have to bring it in to the dealer, but in advance of doing so, I was hoping somebody might be able to shed some light on what's going on.

Is anybody else experiencing this behavior? Any idea what it could be?

- Bob

[wandern]

Any chance it's a malfunctioning exhaust flapper valve? It's located downstream of the muffler, so in the general area you're hearing the sound, and its real purpose is to be effective during the V4/V8 transitions.

[bobbyd]

Thanks for the suggestion, Wandern, I'll def suggest that possibility to the service dept when I finally take it in.

 

Has anyone else experienced this issue?

[Charlieo132]

Might want to take a look at this thread. Do you have Rancho shocks? Mine is currently at the shop for basically the same issue.

 

http://www.gm-trucks.com/forums/topic/154769-has-anyone-had-a-popping-noise-from-under-the-bed-area/

[crushNchowda]

I can assure you the sound you're describing is not the rancho shocks because the first 2014 SLT I had was a non-z71 and made the exact ping/ting sound under light throttle just as the truck went from v4 to v8 & maybe vice versa. This was also a 3.08 equipped truck and I attribute a lot of the odd shifting and throttle behavior to that combo.

 

I don't know what it was, could have been valve in exhaust as others mentioned, but my new all terrain model w/ 3.42 (and ranchos) does not do it. And now I can't notice even if it did because I have a catback.

[bobbyd]

Mine is an all terrain with 3.42 gears. I do have the Rancho shocks, but I don't think they'd be the source of the issue given the apparent relationship between the offending sound and switching from v4-v8.

[CorvetteOJ]

Any chance it's a malfunctioning exhaust flapper valve? It's located downstream of the muffler, so in the general area you're hearing the sound, and its real purpose is to be effective during the V4/V8 transitions.

+1 I agree, I would bet it is the valve. When I had my exhaust modified, my exhaust guy told me he has removed numerous valves, especially from the late model Camaros. After a few miles, they start pinging, flapping, especially when the AFM changes modes. As I mentioned in another, my entire factory system, from the last cat back is gone. Replaced with a 22" magnaflow and two straight pipes coming out the back. No problems, looks good, sounds good, and I don't have to worry about the stupid valve.

[suess13]

so is this a exhaust valve that closes when v4 mode kicks in to add back pressure to the exhaust?

[gkhatta]

make sure it is not you're rear end. although it is rare case, my rear went bad and the torque change going in between v4 and v8 knocked the rear end gears and made a noise as you have described. this is probably not the problem in your car, but it happened to me soo check it to make sure

 

Sent from my SCH-I545 using Tapatalk

 

 

[GMCustomerService]

Pinging, popping, and grinding? We definitely didn't have those verbs in mind for you on a brand new truck! I see you're gathering insights from other members of the community; be sure to keep us posted on when you do decide to visit your dealership as we're here to provide any additional support we can!

 

Regards,

Sarah (Assisting Jennifer)

GM Customer Care

[mzodarg]

Mine has started to do the same thing, it appears to be more audible in colder weather.

 

Sarah- I'm Sure GM never planned the issue, but I'm also sure that the R&D/engineering was sub par to say the least.

 

My fix will be to completely remove the factory exhaust from the catback. Three CATs, Really????

 

Mike

[2014 Sporty Shorty]

Mine did this back when I had AFM. Even after I redone my whole exhaust it was still there ( The valve was taken out). After I got my Diablo Trinity installed and disabled the AFM in the tune, the pinging, hesitations, and the overall annoyance of having AFM are long gone.

[bobbyd]

I posted my update in another thread that seemed like it might be related, but since GM CS asked me to keep them posted, I'm adding it here too:

 

I finally took my truck to the dealer last week. The tech believed it was a piece of plastic rattling on one of the rear shocks. When I asked why it only happened in V4 mode or when going from V8->V4 mode, I was told it was "resonance from the exhaust causing the loose plastic on the shock to vibrate". Ok, whatever. Two new rear shocks - same damn annoying sound.

 

Bringing the truck back this week.

[Ray T.]

I HAVE A 2014 1500 SIERRA CREW CAB THAT IS DOING A SIMILAR THING. THE DEALERSHIP TOLD ME IT WAS A CHANGE GM MADE TO THE DRIVE TRAIN. MINE HAPPENS MOSTLY WHEN I'M SLOWING AND THEN JUST BEFORE HAVING TO COMPLETELY STOP, TAKE OFF AGAIN. NOT A HARD ACCELERATION OR ANYTHING, JUST BACK ON THE GAS. OR AFTER I HAVE COME TO A COMPLETE STOP AND HAVE SAT AT A TRAFFIC LIGHT OR SOMETHING AND START TO TAKE OFF AND IT MAKES A CLUNKING NOISE OF SORTS. MY TRUCK HAS MAYBE 6000 MILES ON IT AND IS NOT RUN HARD. HASN'T HAD ANY MODIFICATIONS TO IT. STILL COMPLETELY STOCK. SOUNDS LIKE THERE IS SLACK IN THE REAR END OR DRIVE SHAFT.

[GMCustomerService]

Hi Ray T.

 

I understand how discouraging it can be to have concerns with a new vehicle. I'd be happy to give your local dealership a call for a second diagnosis. If any assistance is needed, please reach out to us via PM to discuss further.

 

Thank you,

 

Andraya

GM Customer Care