Shake/Vibration FIX

[Bowtie619]

Hey guys,

 

I posted in the giant thread about my fix but I'm sure it's already gotten lost. I think this is important to at least have floating somewhere for someone to search.

 

Symptoms: At 60-70mph I was experiencing a severe shake/vibration. I could usually push out of it at 70+ but it was still noticeable. It was like clock work as soon as I hit up around 60mph.

 

Solution: I got my truck fully inspected before purchase and they noted the vibration. Mechanic showed me a dent in the drive shaft and general wear on the shaft. His recommendation was to replace it. I ordered the part online. The new shaft came fully assembled with new Ujoints and the yoke to slide in. Installation was very easy. I have driven 100 miles since installation and I have ZERO vibration. I hit 60mph and it is very smooth. So the culprit could be the shaft the ujoint or the yoke. Once again this fix worked for me and it may not be the same issue on your truck but I had pretty bad vibrations and they are GONE.

 

Good luck!!

 

*NOTE* I have no warranty so that is why I attempted a fix on my own. I'm sure this problem will still crop up as peoples warranty starts to expire.

Edited March 7, 2016 by Bowtie619

[tnchevy]

Have you taken the truck to 72 mph or higher? If so did it vibrate then? Most people with the vibration problem (including myself) do not have vibes below 70 mph.

[Bowtie619]

Have you taken the truck to 72 mph or higher? If so did it vibrate then? Most people with the vibration problem (including myself) do not have vibes below 70 mph.

 

I have taken it up to 85 with no issues. Cruise at about 80mph to multiple destination with no issues. It's a night and day comparison. At this point the vibration is not partially but completely gone. I've only gone about 100 miles so there is still a chance it could come back but I'm willing to bet there was an issue with the original Ujoints or yoke. Also, when I pulled the yoke out it looked pretty dry. The new shaft had a ton of lubricant in it. Not sure if that could have been an issue as well.

[abominable z71]

 

 

I have taken it up to 85 with no issues. Cruise at about 80mph to multiple destination with no issues. It's a night and day comparison. At this point the vibration is not partially but completely gone. I've only gone about 100 miles so there is still a chance it could come back but I'm willing to bet there was an issue with the original Ujoints or yoke. Also, when I pulled the yoke out it looked pretty dry. The new shaft had a ton of lubricant in it. Not sure if that could have been an issue as well.

 

What ratio is the rear end in your truck? 3.42?

[tnchevy]

There has been quite a few people who have had their driveshaft replaced and it did nothing to cure the vibes. I think you just had a bent drive shaft that caused vibes and the new one fixed it. You said you were having severe vibes between 60 and 70 mph, almost all the complaints on vibes are either above 70 mph or below 45 mph.

[Bowtie619]

There has been quite a few people who have had their driveshaft replaced and it did nothing to cure the vibes. I think you just had a bent drive shaft that caused vibes and the new one fixed it. You said you were having severe vibes between 60 and 70 mph, almost all the complaints on vibes are either above 70 mph or below 45 mph.

I agree, but did they replace only the shaft? Or were the Ubolts and yoke also replaced? Just something to consider. The dent was so small I don't feel like it could have affected the overall spin of the shaft but I could be wrong. Like I said, there is no definite solution for everyone but this 100% fixed my problem. The part was about 350$, with I think a 30% restocking fee on returns. Might be worth the risk to some people who don't have any other options at this point.

What ratio is the rear end in your truck? 3.42?

I'm not sure, is there somewhere I can check this?

[tnchevy]

Glove box. Will say GU6 for 3.42 and GU4 for 3.08

[Bowtie619]

Glove box. Will say GU6 for 3.42 and GU4 for 3.08

GU6

[abominable z71]

GU6

would you say that your vibration was slight at 60 peaked at 65 and reduced to 70 and then basically went away after 70?

[Bowtie619]

would you say that your vibration was slight at 60 peaked at 65 and reduced to 70 and then basically went away after 70?

I wouldn't say it went away at 70+, it felt more like it was pulsating slowly. The rest would be a good description though.

[abominable z71]

This confirms something for me, my suspicion has been that these truck resonate at 39 Hz which means even slight disturbances can cause vibration issues. Which for tire speed peaks at about 75 mph. or 3 times the rotational speed of the tire. Because the rear end ratio is 3.42 in your truck the drive line angular velocity is approximately 39Hz at 65 mph. Confirms the problem is resonance and the body mounts like to transmit vibrations in the 39 hz region. Like you said the dent looked so minor you wouldn't think it would cause issues but if you have a resonance situation even something minor makes it way through. Thanks for the info

[Weeno99]

I'm no engineer but that doesn't sound like there's an easy fix for that?

[abominable z71]

I'm no engineer but that doesn't sound like there's an easy fix for that?

Redesign of the body mounts, which would require more crash testing and expensive qualifications. Makes me wonder if the reason some trucks vibrate and most don't is the batch of rubber the mounts are made from. I've considered purchasing a new set but you'd be in it a 1000 dollars to do the 6 cab mounts. They're a hydraulic shear mount which was patented in 2011 by vibracoustics north america which is owned by Trelleborg, and according to their website they make just about every body mount for every manufacture so I can't see why the would only have issues with this particular truck but who knows. I'm working on a mount to cancel out that frequency that will replace the pucks used for my 1.5" body lift, but the spring rate of rubber is tricky and it's dependent upon the weight of the cab so I'm just throwing a wild ass guess at what that number is plus you have to account for a varying mass from 200 - 1000 lbs depending on passengers. Going to be some trial and error I'm sure.

[EastCoast HD]

Redesign of the body mounts, which would require more crash testing and expensive qualifications. Makes me wonder if the reason some trucks vibrate and most don't is the batch of rubber the mounts are made from. I've considered purchasing a new set but you'd be in it a 1000 dollars to do the 6 cab mounts. They're a hydraulic shear mount which was patented in 2011 by vibracoustics north america which is owned by Trelleborg, and according to their website they make just about every body mount for every manufacture so I can't see why the would only have issues with this particular truck but who knows. I'm working on a mount to cancel out that frequency that will replace the pucks used for my 1.5" body lift, but the spring rate of rubber is tricky and it's dependent upon the weight of the cab so I'm just throwing a wild ass guess at what that number is plus you have to account for a varying mass from 200 - 1000 lbs depending on passengers. Going to be some trial and error I'm sure.

I totally agree with all of this.

 

I wonder how the previous GMT-900 body mounts compare dimensionally. Will they fit?

[abominable z71]

I totally agree with all of this.

 

I wonder how the previous GMT-900 body mounts compare dimensionally. Will they fit?

That's a negative not without some serious adaptation. This is an avenue I'm currently looking into though. at least for the two rear cab mounts. When GM had a problem with frame beaming on the HD they released a redesigned cab mount to fix the issue. Because I have the body lift I can fit the GMT900 cab mount which by the way is the same mount still used on the current production HD platform which doesn't vibrate. The major difference is the new shear mounts bolt to the frame with 2 ears that attach to outer isolator, the interior isolator that carries the mount bolt just passes through a hole in the perch and doesn't actually sandwich either side of the perch see the patent link below. My thought without measuring the through hole on the perch is that it is too big and the lower mounting isolator from the GMT 900 will having nothing to seat against see the other link below. But I think there is enough room to fab an adapter plate that can use the 2 existing holes for the shear mount to bolt into place and carry the GMT900 mount. I thought about giving this a try before replacing all the lift pucks with something else. Below are the two links one that shows how the GMT900 mount works and the other is the patent for shear style mount which is what is currently underneath the K2XX 1500's. If you look up part # 25994881 on a gm parts website it shows it as being the current mount used on 2015 2500 and 3500 pickups and being the replacement mount on the GMT900 trucks as well.

 

http://www.gmtruckcentral.com/articles/bodymounts.html

http://www.google.com/patents/US7389977