New Vibrations

Check front tires for belt slip and balance. did you check front wheel bearings? Does the seats shake more than wheel or dash?

Without pulling the tire off, I pulled and pushed and twisted on the tire and everything feels firm. So I tried to rule out the wheel bearings.

The two spots I really feel the vibrating are the gas peddle, and the rear view mirror. I would have to say that the seats do more than the wheel. There is little to no vibration or shake in the steering wheel.

I was looking today and it looks like the inside of the drivers side tire is wearing very unevenly. I knew the camber was off so the toe was out a little, and that accounts for the uneven tread wear, but the the tread is wearing patchy, and I think that is the vibration.

However, would that account for the vibration getting worse as I accelerate? The more aggressive the acceleration, the worse the vibration, then when I let off the gas peddle, it lessens.

Like when I stand on it while moving at any speed over about 30mph, it's like I am riding a 2 stroke go cart. Then when I let up, it dies down, but does not entirely go away.

If tire is cupping yes that will vibrate increase in speed would vibrate more. Also two vibs seem to be occuring front and rear at high speed. Get some tires and alignment and you will feel great improvement.

I do need new tires; And here is something new. Yesterday I pulled into a hotel for a minute, and as I went to leave (moving forward), there was a squeak and a clunk (in that order) from what sounded like the differential. I stopped and started again and same thing, a squeak and a clunk. I started moving forward again and the squeak went away at 30mph. I tried it again today, and it was gone.

I heard it last week for the first time, but just over looked it. Now it seems to be getting quit frequent.

Are we still thinking tires, or two different problems?

I am now thinking drive train vibration. Need to get on lift and check entire drive train before the squeak clunk leaves you stranded.

So I was driving in today, and playing with the speed to see if I can find where this is happening more, and come to find out, it is only when I am accelerating. When I am coasting, no vibration, and it is at it's worst when I am accelerating between 30 and 45.

I drove through a tunnel today and was stopping and starting to see if I could make the noise happen, and sure enough, I did. When I am accelerating, it almost sounds like there is something rattling around my drive shaft, like a rock or something, but the sound is definattly coming between the middle and rear of the truck.

You found it need U-joints Classic 30-40mph vib. and on acceleration. Needle bearings bad and joint rattles the hollow shaft echos sound.

Took it to a local shop the other day. Tell me if this sounds right, the pinion gear in the differential. It was diagnosed by the ability to turn the rear wheels a fair amount with the truck on jacks and in park.

He further said I have to have change the pinion gear set and the "differential gear set" (which are two separate items).

They are two seperate gears but are usually sold as a set. Ring and pinion check it out with parts house.
Wheel backlash is good test for excessive gear play but only if drive shaft is held not just in park. Grab D shaft see if it moves in park and wheels on ground. Then jack up rear and move wheel if it moves and D shaft does not then play is in diff.

That is more or less what he said he did and sure enough, there was play.

Well, thanks for all of your help. I will post one more after this if it fixes the problem.

Standing by best of fortune
Merry Christmas

What was the fix for your Avalanche? Mine is doing the exact same thing, and I have been to three shops now, and thousands later, vibration is still there, both in pedal and rear view mirror

Drive-line vibrations are almost always the drive shaft. I would remove it and try a used unit from a different car. Here is a guide to help:

https://www.2carpros.com/articles/how-to-remove-a-drive-shaft

If I am off base can you please shoot a quick video with your phone so we can hear the noise, that would be great. You can upload it here with your response.

Please let us know what happens.

Cheers, Ken

Ken, it is not a sound, so video does nothing. I am thinking rear differential, but just had it in the differential shop (very reputable one at that) and only thing they found, was a leaking front seal, and a "black"bearing. They replaced those, and vibration is still there. Also had it at a transmission shop for a week, and they went all through it, with no helpful information, just told me the transfer case motor was binding up, so I had them replace that, and never noticed a difference there as well.

The poster was 10 years ago so I don't know if they will respond. I would raise the back of the truck up and put it on jackstands they start it up and put it in drive so you can watch the driveshaft etc. to see if you can see anything /bent/binding. Be careful of the tires.

https://www.2carpros.com/articles/jack-up-and-lift-your-car-safely

Ken, did that already, and saw nothing unusual.

Can you feel which part of the truck the vibration is coming from front, middle, back? Is the truck raised? Normal size tires?

Cannot pinpoint area, one shop said rear, differential shop said front, nether one could diagnose, stock height, normal size tires.

Does it vibrate in neutral? Is there a speed or RPM it does it more? I have seen torque converters have a problem causing vibrations.

Not that big of a vibration to catch on a test of shifting into neutral on freeway. Feel it more with acceleration, and higher speeds.

I am wondering if the differential fluid is low or needs to be changed. It sounds like the ring and pinion gears are binding. Here is a video so we can check the gears and fluid out:

https://youtu.be/6F26Kir0OCg

Let me know.

I have changed the fluid 3 times now, in less than 50 miles. And last stop was Differential shop, and all checked out there, as well

Hello,I'm Danny
I hate to be the bearer of bad news but the Chevy Avalanche Rear Differentials were prone to problems. I would suggest going to a more reputable differential shop. This is a know fact. You can change the Differential gear oil as long/few few miles as you like but it will not change the problem with the Carrier/Carrier Bearing problems. This is the reason why GM discontinued that model and it's all in the junkyards now.... Hope this helps and thanks for using 2CarPros.

Haha, that's funny, as I see these driving around everywhere, and are scarce in junkyards (trust me, I have a hard time finding parts). And, a "more reputable dif shop"? This is the best one in the valley, look them up AZ Differential

It is really the only thing left. Please let us know what they find.

Just took it in, for yet another differential diagnostic this morning, and another $140 fee, and all checks out good, like the other shop said

I would have the driveshaft balanced next. Its difficult for us to tell without driving it or having a video showing what's going on.

I'm just gonna drive it the way it is. Already over $2,000 in people guessing. Weird as people don't know anything about a 3/4 ton Avalanche

At least this didn't cost you anything. If I could drive it I could figure it out. You close to California?