V4 to V6 shudder

Rick35 · October 2, 2015

GM field service is coming to check out my truck this week. I can't imagine he's going to do something the local techs didn't already do but I hope I'm wrong. Generally there seems to be a focus on a vibration at a particular frequency but it sure feels like more than a vibration. Dealer service already checked and it wasn't what my problem is. They said it had to do with transitioning in and out of v4 prematurely. Sounds like a computer or sensor problem to me but they're the experts.

14silverado4.3 · October 8, 2015

GM field service is coming to check out my truck this week. I can't imagine he's going to do something the local techs didn't already do but I hope I'm wrong. Generally there seems to be a focus on a vibration at a particular frequency but it sure feels like more than a vibration. Dealer service already checked and it wasn't what my problem is. They said it had to do with transitioning in and out of v4 prematurely. Sounds like a computer or sensor problem to me but they're the experts.

Update

Rick35 · October 9, 2015

The GM field engineer checked out my truck today and confirmed that the problem is a vibration in the exhaust. There's a GM tech bulletin from October 2014 that describes adjustments to the exhaust but it didn't work for me in a previous repair attempt. The latest fix is a custom part that GM needs to make. That sounds strange considering there have been 2014's on the road for almost two years. The service guy confirmed that there is something going on with some 4.3's and it is related to switching from V4 to V6. I guess it makes sense that there could be some vibration as the cylinders start up. Maybe its a change in the engine balance during the transition. It is hard to believe that a vibration can be that pronounced. So I'm on hold again waiting for the part.

tstodda · October 9, 2015

The GM field engineer checked out my truck today and confirmed that the problem is a vibration in the exhaust. There's a GM tech bulletin from October 2014 that describes adjustments to the exhaust but it didn't work for me in a previous repair attempt. The latest fix is a custom part that GM needs to make. That sounds strange considering there have been 2014's on the road for almost two years. The service guy confirmed that there is something going on with some 4.3's and it is related to switching from V4 to V6. I guess it makes sense that there could be some vibration as the cylinders start up. Maybe its a change in the engine balance during the transition. It is hard to believe that a vibration can be that pronounced. So I'm on hold again waiting for the part.

Good luck! Based on the fixes they had only a month ago it sounds like they are still paying a lot of attention to this and trying to fix it.

Rick35 · October 9, 2015

When I heard the word "dampener" used I googled it and found there is a "damper" at the exhaust in the pipe to reduce vibration/sound generated in V4 mode. I still find it strange that this is a problem still after two years with 2014's on the road. And, there have been AFM vibration/sound issues in prior years. I found posts from 2007 that sounded similar to this problem and not just with Silverados or Sierras.

I was getting nervous that there wasn't going to be a solution after yesterday's trip to the shop. I' m encouraged by the efforts and I'm satisfied with the attention from the dealership and GM. The word from the field service engineer was that he was confident of the fix. I was especially happy to hear that it was definitely not in the engine which worried me about future wear and problems after the warranty is up. After the problems GM brought on themselves previously it does look like they're doing the right things to make it right.

GMMediumDutyMQ · October 9, 2015

God, I really hope they make that fix universal...I'm about to be through my warranty and this is the LONE complaint I have with my truck.

Rick35 · October 10, 2015

I would think GM would extend the warranty for that if you have been trying to get it fixed.

What's interesting is that I didn't have any problems until around 11k miles. I'll get more info on the fix when

I go back in. They thought it would be in a week or two.

14silverado4.3 · October 12, 2015

I just spoke with a local dealership here in Ohio. They have a test pig coming into their shop on Wednesday to fit an experimental kit for V6 / V4 vibration. A GM engineer will be on site to do the install. He and I will be in contact then to discuss the kit in more detail. If all goes well, he will personally contact my dealership to oversee the ordering and installation of the kit. This guy seemed to care more about fixing my truck than my dealer I bought it off of.

Rick35 · October 12, 2015

That's too bad about your dealer. Mine has been great. My truck is going in for the procedure on Thursday. I've got a loaner lined up and will drop it off Wednesday night. It will be out of recovery and ready to go home Thursday night and hopefully cured.

Rick35 · October 12, 2015

If I can self diagnose I think the issue is the exhaust adaptive valve. I just googled it and there are a lot of postings at various forums. Its purpose is to stop noise and vibration and in particular "V4 drone" and if its the culprit its doing just the opposite. I hope to get a definitive answer when the truck is in for the fix. Its starting to make sense. I hope.

14silverado4.3 · October 15, 2015

If I can self diagnose I think the issue is the exhaust adaptive valve. I just googled it and there are a lot of postings at various forums. Its purpose is to stop noise and vibration and in particular "V4 drone" and if its the culprit its doing just the opposite. I hope to get a definitive answer when the truck is in for the fix. Its starting to make sense. I hope.

Tag for the update.

Rick35 · October 16, 2015

I picked up my truck tonight and there was no indication of shuddering on the way home. I need to drive it a bit more but I think they fixed it! There was no part number for the damper on the repair order but I would think GM will make it available to dealers now that they have a fix. I felt kind of like a guinea pig in all this and I'm still surprised they hadn't figured it out until now. Hopefully they can get the fix out to others and we can get back to enjoying our trucks.

14silverado4.3 · October 16, 2015

Can you send a pic or tell us what the fix looks like?

Rick35 · October 17, 2015

I crawled under the truck tonight and can't find anything new. The adaptive valve is looking original and that's what I thought was the culprit. There was a rubber mount that looked kind of new but I don't know if thats what they call a damper. All I know is that I'm not feeling the shudder.

Rick35 · October 17, 2015

I tried again and found a brown cylindrical object attached to the exhaust in front of the catalytic converter. After not finding anything earlier I went back into the house and googled dampener again and I found a photo of an exhaust dampener from a few years ago. Mine looks just like it. From what I found from the old post it sounds like there's weight in the cylinder that dampens the vibration of the exhaust. The service order I received from the field engineer correctly called it a dampener and not a damper which is something different altogether. I'm new to the forum and certainly new to uploading photos and hopefully the photo loads correctly.

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