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Intermittent Front End Highway Vibration

03z71

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03z71 Enthusiast

03z71

Posted
Posted

2003 1500 Silverado ECSB 4x4, 5.3L all stock with exception of 285/75R16 BFG ATKOs.

 

I have an intermittent vibration/humming in the front end above 50 mph or so. It is kind of a low pitched hum with a vibration you can feel in your feet. It will start up and pulsate at maybe one pulse per second, speed up to maybe 4 pulses per second and slow back down again - all at exactly the same speed. It will do it with the cruise set, under acceleration, coasting, or turning (as much as possible above 50 mph). The pulsing speeds up and slows down completely unrelated to speed or RPM. On the highway, it might do it for 5 minutes straight at various pulse speeds and stop for 20 minutes.

 

The truck has 125,000 miles on it. I actually experienced this same problem while the truck was under warranty (back in 2004). The useless dealer just rotated the tires (stock Firestone Wilderness ATs at that point) the two times I brought it in and proclaimed that they fixed it. The first time, it quit for a couple thousand miles and came back again. The second time, it mostly quit for about 90,000 miles (would maybe do it a couple times a year briefly and then quit)... When it started doing the same thing again recently on a much more frequent basis, I rotated and rebalanced the tires and replaced the front wheel hub assemblies (the passenger side was completely shot - tons of play top to bottom). That didn't help. I do have a very intermittent 4x4 problem - likely either the encoder motor or sensor that has thrown a code (but of course not in the PCM, so I can't see it - the DIC will say "Service 4wd" once in a rare while in the winter when it's wet out). I'm guessing that's unrelated, but who knows.

 

At this point, I'm trying to figure out if its worth fixing or not. If I keep the truck, I need to get this vibration issue fixed as well as the t-case problem. With deals on the 2013s and the new 2014s around the corner, I might replace it. I have an appointment next week to have it looked at, but I'm scared of paying $ to get one thing fixed only to find out that didn't take care of it (I was hoping it was the front wheel bearings)... So I'm desperate to try to figure out what this could be and if it's going to be worth me having it fixed on a nearly 11 year old truck.

 

Thanks for reading my novel and for any suggestions or help!

03z71 Enthusiast

03z71

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Nobody has any ideas, huh? That's what I'm afraid I will hear from a mechanic. It's so strange that the vibration is independent of speed and engine RPM...

FrankenChevy Enthusiast

FrankenChevy

Posted
Posted

I will have to admit that is a strange one.

 

 

If rotating the tires did not change anything, and the hub bearings did not fix it, then the problem may be in the front differential. The front axles on these trucks spin at all times. They disengage and engage inside the diff. You can check the condition of the fluid. Put a few drops on white cardbord and see what it looks like. Some have had problems with the front diffs on these trucks.

bossier62guy Senior Enthusiast

bossier62guy

Posted
Posted

The useless dealer just rotated the tires (stock Firestone Wilderness ATs at that point) the two times I brought it in and proclaimed that they fixed it. The first time, it quit for a couple thousand miles and came back again. The second time, it mostly quit for about 90,000 miles (would maybe do it a couple times a year briefly and then quit)...

 

It's so strange that the vibration is independent of speed and engine RPM...

 

These statements are making it difficult to obtain help here but don't give up just yet. Are you the original owner of the truck? Has it ever been in any accidents? Did all of this start with this set of tires? It's odd that a tire rotation made it disappear for a while when you say the vibe is not related to vehicle speed or engine RPM.

As far as the 4wd problem goes it's probably the transfer case switch. There are many documented cases of those causing the 4wd drive light to come on. From what I've read there may be some cold or fractured solder joints on the circuit board. Many people have fixed it by opening up the switch and resoldering the joints.

I personally wouldn't get rid of a vehicle for such minor issues.

03z71 Enthusiast

03z71

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I am not the original owner. I bought it in January of 2004 when it had 25,000 miles on it and was a little over a year old. It has never been in any accidents. When it had (what I believe was) the same issue almost 10 years ago when under warranty, I'm 99.99% sure that the tire rotation did not solve anything - it was pure coincidence. At that point, it did it so rarely that the dealer was able to use the tires as a scapegoat. Since it was (and is) not related to vehicle speed, I was pretty sure then that the tires had nothing to do with it.

 

I'm not really concerned about the 4wd problem. I think it's the encoder motor sensor rather than the switch. Neither are that expensive though and not reason to get rid of the truck. It's the vibration issue that could be a relatively cheap thing to fix but harder to diagnose. Since it sounds like the front axles engage and disingage inside the front diff, that could be the most likely culprit. I wonder how much a front diff rebuild costs if that turns out to be the problem... So the front driveshaft only turns when in 4wd?

waumo1 Enthusiast

waumo1

Posted
Posted

If the vibration is independent of speed and rpm, how could it be any of the rotating components of the vehicle?

bossier62guy Senior Enthusiast

bossier62guy

Posted
Posted

That's why we're here....to do a little brain storming. Have you done anything other than take it to the dealer to get checked out? Is the vibration felt at your feet the same rate the hum is heard? This may be a crazy question but, anyway you can get an audio clip of it? It's going to be tough for us without some video/audio.

03z71 Enthusiast

03z71

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Brainstorming is good. I appreciate any ideas you guys can come up with. I've not done anything other than replace the wheel hubs and rotate and balance the tires. I was hoping it was the wheel bearings but that didn't do it. I've not had it to a dealer or mechanic for the noise/vibration specifically since the warranty visits. I'm taking it to a mechanic tomorrow to see what they can find out. I will try to get a sound recording but fear it will be too hard to hear in a recording. We'll see.

FrankenChevy Enthusiast

FrankenChevy

Posted
Posted

If I am correct, and the engage mechanism is in the front diff, then it sounds like it is trying to "engage" and that is the noise and vibration. It is independent of speed and rpm because it is not fully engaged. I am wondering if a fluid change and some synthetic fluid would cure this. I don't think the front diff requires synthetic fluid and not sure if there are any drawbacks. You may want to check owners manual. You can also feel the front diff housing where the axles go in after a good drive, see if it is getting hot. Also might try runnig a bit in 4 wheel drive, high, low ect, stir up the fluid good.

 

Let us know how you make out.

 

 

.

03z71 Enthusiast

03z71

Posted
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The truck is now at a trusted mechanic's shop. I tried to get a recording of the noise on the way over there, but was only up to highway speed for 1/2 a mile and it didn't even do it. Interesting thought about the front diff not being fully engaged. When I talked to the mechanic this morning (without him having heard it yet), he said he wants to look at the front of the rear driveshaft since it is the only driveshaft rotating all the time. I did have the front diff fluid changed not too long ago, but did not use synthetic because it is specifically not recommended. It had something to do with the vent tube or something like that as I recall as to why GM says not to use synthetic.

 

I'll let you guys know what I find out from the mechanic. Fingers crossed he can figure it out more easily than I can.

Shaners Senior Enthusiast

Shaners

Posted
Posted

The only time I had a similar problem the culprit turned out to be the carrier bearings in the driveshaft. I am not sure if your truck would have a 1 or 2 piece driveshaft though.

  • 1 month later...
edd189 New Member

edd189

Posted
Posted

I signed up just to respond to your post. I have a similar issue, with a weird low frequency vibration and I believe its related to the front end as well. When about 50+ mph, the pulsating vibration occurs. At highway speed, if I go from 2-Hi to AUTO, it goes away. When I go back to 2-Hi it comes right back. So could it be related to your front diff clutch attempting to engage? Is there any way to tell if this is what's occurring?

 

What did your mechanic say?

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