Grinding/ slightest vibration/ rpm bouncing

[AllenW2018]

I’m going to describe this to the best of my ablitly, and see if anyone else has experienced this, or has any thoughts on it. Ive been riding like this for months because I haven’t had a chance to put it in the shop. 

 

 

Truck: 2014 Sierra 1500 4x4 all terrain slt w/ 6.2.     4 inch lift. 33” tires. 20” wheels. 

 

The sound: sounds like something rubbing/ slightly grinding. It has to be something rotating. It can be a faint noise or something  loud that really grabs your attention. 

 

When it occurs: 

When everything starts warming up nicely, generally somewhere around 2 miles into trip. it’s by far the worst once you get to the speed you desire and stay there ( with cruise or just using pedal ). happens on occasion when accelerating up to speed, but not near as often.  It never does it when slowing down. 

 

Duration: 

there is no pattern to it whatsoever. It could make the noise for .2 seconds. Stop for 12 seconds. Grind for 4 whole seconds. Stop for .5 seconds. You get the picture.  

 

Its continuous, in a sense that if you have a 100 mile trip, it’s going to continuously start and stop the whole way. 

 

Other things to note: 

 

i have noticed that as soon as I hear the sound start, I can let off of the gas, or give it a little more and it immediately cuts the noise out. As soon as I hold the pedal and maintain speed, it starts back up. 

 

The other her thing I’ve noticed is that the rpm needle is steadily moving at all times. Example, running 70 on perfect flat smooth road, cruise on, the rpm needle is Jumping back and forth about 100 rpms. 

 

 

 

I have tried to be detailed and thorough, so let me know what you guys think if it sounds familiar. 

 

[silveradosid]

i hope some one can make a suggestion my 2014 chev 5.3 6 speed does the same thing

[Doublebase]

So it's coming from the engine?

 

Water pump? Alternator? AC pulley? 

 

Rotational noise in the engine usually points to those types of things...the idler pulleys, water pump, alternator, tensioner, anything that spins. Try removing the belt and check for a roughness/bad bearings. 

 

I suppose if your truck has over 50,000 miles, any of the above is possible.

[AllenW2018]

2 hours ago, Doublebase said:

So it's coming from the engine?

 

Water pump? Alternator? AC pulley? 

 

Rotational noise in the engine usually points to those types of things...the idler pulleys, water pump, alternator, tensioner, anything that spins. Try removing the belt and check for a roughness/bad bearings. 

 

I suppose if your truck has over 50,000 miles, any of the above is possible.

Forgot to mention this. I’ve had several people ride with me and listen to it. Everyone has said they think it’s coming from directly under them in the backseat. Sounds like that to me as well. It’s been doing this for almost a year and hasn’t gotten any better or worse. 

[Doublebase]

19 minutes ago, AllenW2018 said:

Forgot to mention this. I’ve had several people ride with me and listen to it. Everyone has said they think it’s coming from directly under them in the backseat. Sounds like that to me as well. It’s been doing this for almost a year and hasn’t gotten any better or worse. 

Oh ok, so more like driveline. Hmm. U joint sticking a little bit, maybe? Oh wait you said you have a 4" lift...that definitely changes driveline angles and stresses u joints. Maybe put it in neutral and coast when you're experiencing it, see if it goes away. Maybe pull the drive shaft out and check the ball joints. Just some thoughts. More simple type of stuff than condemning the transmission, etc.

[AllenW2018]

2 hours ago, Doublebase said:

Oh ok, so more like driveline. Hmm. U joint sticking a little bit, maybe? Oh wait you said you have a 4" lift...that definitely changes driveline angles and stresses u joints. Maybe put it in neutral and coast when you're experiencing it, see if it goes away. Maybe pull the drive shaft out and check the ball joints. Just some thoughts. More simple type of stuff than condemning the transmission, etc.

Just went to town and tried putting it in neutral. It responds the same way as letting off the gas. It immediately cuts the noise out and doesn’t pick back up until you put it in drive and get back to speed. Same goes for just letting off the gas. You can coast all the way down and it never makes a sound. 

[Dr Awesome]

Transfer case is under there around that area, could be something in there.  Have you tried putting it in 4WD and seeing if it changes it at all?  I just did my transfer case fluid and there was quite a bit of gunk, and I only have 3k on it.  Might not be related at all, but if you haven't done the fluid in there you could check that out and see if there are any signs of an issue in there.

 

https://www.gm-trucks.com/forums/topic/213361-changed-my-transfer-case-fluid-at-3k-surprised-at-the-amount-of-gunk-pic/

[Doublebase]

4 hours ago, AllenW2018 said:

Just went to town and tried putting it in neutral. It responds the same way as letting off the gas. It immediately cuts the noise out and doesn’t pick back up until you put it in drive and get back to speed. Same goes for just letting off the gas. You can coast all the way down and it never makes a sound. 

Sounds like when the driveline is asked to do something/stressed, it makes a worn bearing noise. Could be anything from bearings in the differential, u joint, bearing in the transmission, transfer case, torque converter, flexplate cracked. I don't know, but I'd start with the simple stuff. Check your transmission fluid, transfer case fluid. Differentials. Maybe remove your driveshaft and check the u joints. 

 

Check your heat shield too, sometimes when the engine is put under load it can twist enough to cause a heat shield noise that vibrates under the passenger compartment. 

[eric8610]

I have a 14 GMC Sierra 4x4 and it sounds like I am having the same issue.

 

It sounds like I’m driving over rumble strips on the road. It usually lasts for 2 - 3 seconds and it then it goes away. Then the noise will return in another 10 or 15 seconds. It seems like it does it the most just cruising when light on the throttle. The RPMs do the same shutter too. The tach will bounce 100 RPMs up and down.

 

[AllenW2018]

18 hours ago, eric8610 said:

I have a 14 GMC Sierra 4x4 and it sounds like I am having the same issue.

 

It sounds like I’m driving over rumble strips on the road. It usually lasts for 2 - 3 seconds and it then it goes away. Then the noise will return in another 10 or 15 seconds. It seems like it does it the most just cruising when light on the throttle. The RPMs do the same shutter too. The tach will bounce 100 RPMs up and down.

 

Yeah I feel pretty confident that it’s the same issue. If it eases your mind any, mine has been doing it for a year and hasn’t gotten any worse. I haven’t had time to put it in the shop for it because it takes for ever for our local dealership to do anything. 

 

If if you happen to get it looked at/ diagnosed/ or fixed, please keep me informed. I may have time in a week or 2 to put mine in the shop. 

[scott.moody.9401]

Yep. Happened to me. Fixed:

 

https://www.gm-trucks.com/forums/topic/213147-8-speed-issue/

 

 

https://r.tapatalk.com/shareLink?url=https://www.gm-trucks.com/forums/topic/213147-8-speed-issue/&share_tid=213147&share_fid=33003&share_type=t

 

Sent from my SM-T817V using Tapatalk

 

 

 

 

[Jeremy Ek]

On 7/24/2018 at 1:09 PM, AllenW2018 said:

Yeah I feel pretty confident that it’s the same issue. If it eases your mind any, mine has been doing it for a year and hasn’t gotten any worse. I haven’t had time to put it in the shop for it because it takes for ever for our local dealership to do anything. 

 

If if you happen to get it looked at/ diagnosed/ or fixed, please keep me informed. I may have time in a week or 2 to put mine in the shop. 

what did u ever figure out on this issue? im experiencing the same thing

 

[jpfanner]

My 2014 started doing this about 10,000 miles ago. Identical. I've been searching and the intenet for months and finally found this thread! Did anyone find out what the fix is?  Isee the thread about the 8 speed transmission but that issue doesn't seem quite like what us on this thread are experiencing. Man I hope someone responds with "dude your heat shield is just vibrating off the bottom of the cab!" I also, have another odd noise that sounds like a wheel bearing hum but I cannot get any play out of the front wheels and I did change one hub already for another reason. Anyway, any help or incite would be greatly appreciated. 

Edited February 1, 2020 by jpfanner

[tlaw91]

Too easy

PIT5404F GM bulletin

Passive exhaust valve rattle

Replace basically the back half of your exhaust. The spring loaded deal after the muffler is making racket it V4 mode. Replace them a lot at the dealer.

You’re welcome

-Friendly neighborhood GM tech


Sent from my iPhone using Tapatalk

[jpfanner]

2 minutes ago, tlaw91 said:

Too easy

PIT5404F GM bulletin

Passive exhaust valve rattle

Replace basically the back half of your exhaust. The spring loaded deal after the muffler is making racket it V4 mode. Replace them a lot at the dealer.

You’re welcome

-Friendly neighborhood GM tech


Sent from my iPhone using Tapatalk

 

I have a Borla cat back exhaust and the AFM/DOD disabled. However it does sound like to me that it's coming from the back half of the truck. But if its a driveline issue somewhere I think those always sound like they are behind me probably just due to the properties of sound dynamics and that I hear it a lot more over 30mph but at steady, low rpm cruising, or when lightly accelerating out of a turn.