Information on Vibration Analysis and Diagnostic – 2014-2015 GM Trucks

[14silverado4.3]

This is not a TSB that I can tell.. If it is a TSB then we can take it to my dealer, they are calling it a PI and according to my dealer this don't mean sh?#

[saafrican]

Okay. I got my truck back from the dealer .They called in the GM field service tech , used the PICo vibration instrument and found the following .

Rear shock faulty , replaced

Rear tyre out. Of road force tolerance ,replaced

They said it was better , but ??????

 

When I collected the truck a week later , I referred the dealer service manager to the vibration service bulletins that's been posted here .

He opened a file ? Yip exact same file ,on record

 

The GM field tech. Said GM are aware of the vibration on 2014/15 V6 trucks when in V4 econo mode !

They don't have a fix !!

Are working on a solution !!!

And will contact me when they have a fix !!!!

Which could be in about ?????

4 months

5 months

6 months

Some time ???????

And they will contact me with a fix

 

Took my truck home after the repairs ???

It still vibrates in V4 Eco mode

Just like before .

 

The dealer that sold me the truck ( ED MORSE Sawgrass ) have been FANTASTIC .

I really appreciate the effort and attention , thanks guys .

 

But my truck still vibrates , and it's GM s problem to solve !

So do I ...........

Now drive it and shut up ?

Trade in for a 2015 and hope it doesn't vibrate . There are more silk smooth V6 trucks than ones that do vibrate .

 

Or wait for a 2016 model ? There is a rumor that GM have changed the engine mounts . And chassis ?

Any body any thing more about changes ?

Which should have fixed this vibration .

 

That's it .

 

Love my truck every time I look at it , and drive it

UNTIL IT VIBRATES IN V4 Eco mode

[EastCoast HD]

It only vibrates in V4 mode?

 

Consider yourself lucky!

[STAYBG]

Yes because of this well written article I was able to identify one of my issues. My shocks were produced before the A14743C date. I removed them and checked and sure enough when compressed they have no resistance for the first couple of inches if shock rod movement. I can also see grease leaking from my U-Joints, the one on the front propeller shaft and the front U-Joint on the rear propeller shaft (drive shaft) is leaking the worst.

i would be willing to be if u have grease or diff fluid at the ujoints then the driveshaft is out of balance causing premature wear on the seals. Edited September 2, 2015 by STAYBG

[Seth_Man]

now the the pico scope has been in all dealers for a few months now its become much easier and faster for us to track down the vibrations going on in these trucks. vibration problems are becoming few and far between these days.

[black00ta]

I saw this article in Indentifix a few months ago and actually printed it off but was unaware it was available on teh internetz. haha

[fireaxxe]

Alright guys, went ahead and pinned the thread but I also moved it to the k2 troubleshooting area. Hopefully others will see it at the top before posting. Thanks to the OP for the link, this is a big help!!

No problelm and thanks for pinning it.

[fireaxxe]

My dealer has been no help. I am still waiting on my muffler parts to come in. I picked up my truck thinking they had at least ran a diagnostic vibration analysis using the pico scope and got the old "could not duplicate issue". I am calling GM customer care and doing my own analysis using this information and wanted to share my findings.

 

1. This issue is cumulative. Due to the stiff frame and design of the body mounts, engine and transmission mounts these vibrations are being collected and amplified. If you have a Z71 the stiff suspension does not help.

 

2. The interior/headliner- is very quiet and I have isolated an issue with the headliner. It seems as if there is a void space in the rear between the headliner and the cab roof that transmitts and magnifiy a droning/vibration sound. This occurs with natrual road noise and vibrations. I removed the trim and pulled the headliner and filled this space with carpet padding. This cured that issue and I am very happy with this mod.

 

3. Tires- are an issue. I had my tires checked rotated and balanced by a tire shop and they rolled two tires into the show room and asked me if I had any abnormal noise or vibration. Of course I said yes. These two tires, taken off the front, had major sawtooth pattern on the inner tread area. I dont know what is causing this but I think its air pressure. After these were rotated to the back and balanced, I put 38 psi and have been driving for about 400miles and the vibration I was hearing and feeling is all but gone!! The best part of this was it was free.

 

4. Body Mounts- seem to change the feel of the road and how the truck responds to vibration. If I set the torque to 52 Ft. Lbs it muffles the vibrations but the truck feels sloppy and there is a strange sound that road noise causes in the cab. At 65 Ft. Lbs it feels sound much better. I did the cab/body mount reset procedure and not sure if that changed anything but the mounts are a factor in all of this. I am still trying to find the sweet spot this this issue.

 

5. Exhaust- the v4 droning and vibration was much better after I repositioned the exhaust collector located behind the last catalytic converter. It seem to be in a bind and when I loosened the clamp the pipe seemed to "relax" and when I retightened the clamp I made sure it stayed in this position. The v4 mode is much better and the "buzz" that I was feeling at idle is gone. I still have a vibration while in v4 and decelerating. I think this issue is the engine/transmission mounts softening up after being pounded by v4 mode and the increased heat under the hood for almost 30k miles.

 

Now the truck feels normal and is pretty close to the new feel I had when I first got it. It is pretty smooth on the highway now and has that "cadillac" feel most other truck owners brag about. I hope this helps the only issue left is the vibration during v4 AFM mode on deceleration but will see if GM comes out with a fix for this soon. Hope the rest of the information helps.

[fireaxxe]

Update: Final parts came in the dealer installed a new exhaust sounds much better but no change with the v4/deceleration vibration. I did check my driveline angles and they were slightly off. You can do this with an iphone. Just download a level bar app and use the phone as an angle finder. The iphone 5s is a great leveler due to its smooth metal edges. I then proceded to change the angle by shimming the transfer/transmission case mount and also the rear axle. This smoothed out the ride even more. There is about 15%-20% vibration left that I would like to get rid of. And it is not the tires. THIS IS ALL RELATED TO THE REAR AXLE!!! The real axle angle adjustment was the only thing that changed the vibration the most. If I angle it down its worse if I angle it up its much better but never goes totally away. I am going to say the pinion/ring gear lash adjustment is off.

[southern_sierra]

My dealer has been no help. I am still waiting on my muffler parts to come in. I picked up my truck thinking they had at least ran a diagnostic vibration analysis using the pico scope and got the old "could not duplicate issue". I am calling GM customer care and doing my own analysis using this information and wanted to share my findings.

 

1. This issue is cumulative. Due to the stiff frame and design of the body mounts, engine and transmission mounts these vibrations are being collected and amplified. If you have a Z71 the stiff suspension does not help.

 

2. The interior/headliner- is very quiet and I have isolated an issue with the headliner. It seems as if there is a void space in the rear between the headliner and the cab roof that transmitts and magnifiy a droning/vibration sound. This occurs with natrual road noise and vibrations. I removed the trim and pulled the headliner and filled this space with carpet padding. This cured that issue and I am very happy with this mod.

 

3. Tires- are an issue. I had my tires checked rotated and balanced by a tire shop and they rolled two tires into the show room and asked me if I had any abnormal noise or vibration. Of course I said yes. These two tires, taken off the front, had major sawtooth pattern on the inner tread area. I dont know what is causing this but I think its air pressure. After these were rotated to the back and balanced, I put 38 psi and have been driving for about 400miles and the vibration I was hearing and feeling is all but gone!! The best part of this was it was free.

 

4. Body Mounts- seem to change the feel of the road and how the truck responds to vibration. If I set the torque to 52 Ft. Lbs it muffles the vibrations but the truck feels sloppy and there is a strange sound that road noise causes in the cab. At 65 Ft. Lbs it feels sound much better. I did the cab/body mount reset procedure and not sure if that changed anything but the mounts are a factor in all of this. I am still trying to find the sweet spot this this issue.

 

5. Exhaust- the v4 droning and vibration was much better after I repositioned the exhaust collector located behind the last catalytic converter. It seem to be in a bind and when I loosened the clamp the pipe seemed to "relax" and when I retightened the clamp I made sure it stayed in this position. The v4 mode is much better and the "buzz" that I was feeling at idle is gone. I still have a vibration while in v4 and decelerating. I think this issue is the engine/transmission mounts softening up after being pounded by v4 mode and the increased heat under the hood for almost 30k miles.

 

Now the truck feels normal and is pretty close to the new feel I had when I first got it. It is pretty smooth on the highway now and has that "cadillac" feel most other truck owners brag about. I hope this helps the only issue left is the vibration during v4 AFM mode on deceleration but will see if GM comes out with a fix for this soon. Hope the rest of the information helps.

Hello Fire

What makes a Z71 stiffer than the regular 4x4 is it just the rancho shocks or does the Z71 have stiffer front coil springs. I changed out my ranchos to the black regular 4x4 shocks and they helps soften the ride just a bit.

Thanks

[fireaxxe]

I am not sure about the coil springs but I know the shocks/struts are stiff.

[fireaxxe]

Hello Fire

What makes a Z71 stiffer than the regular 4x4 is it just the rancho shocks or does the Z71 have stiffer front coil springs. I changed out my ranchos to the black regular 4x4 shocks and they helps soften the ride just a bit.

Thanks

I found a better answer. I have an ALLData service and repair account and I checked the part numbers for the coil springs, leaf springs, shocks/struts, and front stabilizer. There are several different RPO codes and different part numbers listed based on configration and options. One specific option that I see is the Enhanced Towing Package which gives you different springs and stabilizer bar. Hope this answers your question.

[southern_sierra]

I found a better answer. I have an ALLData service and repair account and I checked the part numbers for the coil springs, leaf springs, shocks/struts, and front stabilizer. There are several different RPO codes and different part numbers listed based on configration and options. One specific option that I see is the Enhanced Towing Package which gives you different springs and stabilizer bar. Hope this answers your question.

Thanks for the info. When I get time I'am going to the dealership and get the parts man to check the part numbers of my coils and stabilizer against a regular 4x4 (non Z71) without any tow package. Just curious

[MBalck]

There is a new vibration scope that GM engineers are using. If you were turned away with them saying the truck is within spec with the PICO scope, take it back and demand the other scope to be put on your truck.

[fireaxxe]

There is a new vibration scope that GM engineers are using. If you were turned away with them saying the truck is within spec with the PICO scope, take it back and demand the other scope to be put on your truck.

I can see that happening especially on my truck. It seems to have good days and bad days. For instance yesterday it was pretty smooth as I drove it to the dealership. The only thing that is consistent is the vibration when cold. For the first 10 miles its very noticable I am being told that its the tires. The 50-40 mph vibration on deceleration is also pretty standard.