AWD Chevy vibration - 50+mph

[45Kevin]

Another vote for u-joints here.
Just take off the two drive shafts and check/replace them.
The bad tires that you replaced are probably unrelated to the vibration.

 

[dleeallen]

Ok, been a while since I've updated. I had the tires all road force balanced. All were good. I don't remember the numbers, but all under 20 I think. So apparently that isn't the issue. I brought it to a local 4x4 shop that specializes in Land Rover work. Good people. I used to go out with them when I had my CJ7. They pulled the driveshafts and found the front rear shaft u-joint binding a little. They replaced both on the rear shaft and I gave it a try. The vibration changed. Became very present at 35-45+. Not sure why it changed like that but back it went and they sent the shafts out to check balance / true. The rear was bent. Had a small hop. The driveshaft shop rebuilt it with a new center section. Picked it up today and only drove a little. Snow storm here so the roads are ****ty. Initial impression is it's better. Hoping it is.

 

[RVflyfish]

Not to thread jack, but I have an intermittent vibration at freeway speeds since I lifted my Astro 4". If I floor it so it kicks down a gear or two, then lift the throttle, it usually goes away. I'm thinking it could be because I didn't lengthen the driveshafts when I did the lift. Does that make sense to anyone? Did you lift yours?

 

[dleeallen]

Mine is stock height still. Waiting to solve this first. I would check engine/trans mounts for movement. Thinking you are getting u joint angle change under load causing the vibration.


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[motimbo]

dleeallen ... Hope the rebuild did the trick.

RVflyfish ... You may want to look at the pinion angle at the rear diff. I've been lurking the Astro forums for a few years and remember reading some people have to install angled shims to rotate the differential when lifting over 2".

 

[RVflyfish]

Dleeallen and Motimbo, thank you both. I'll check the mounts. I also remember reading about shims on the Astro forums. I'll have to revisit there.