1999 Blazer w/humming vibration in front end

Driving from 30mph to highway speeds I can hear a slight humming from the front end along with vibration sometimes in the floorboard. It isn't loud or anything, I just know it is there and that it is a new
sound. After looking at posts for awhile, I have seen suggestions that the differential is engaged to bad wheel bearings. I can say that it is quiet at low speeds. What do you guys suggest I look at first?
Thanks, John Manner 1999 Blazer 4.3L 4x4 (AutoTrac) 97,000 miles
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We have the same truck with the same problem, started out around 90k as a little hum, now its so loud you cant hear the radio at 60mph and it shakes like hell. Get ur front wheel bearings checked out. Our Jimmy has 97k on it now, so you still probally got awhile.

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Per John Manner:

When it happened on my 'burb, I figured a wheel bearing was on the way out - at least it *sounded* like that.
Turned out tb a scalloped tire. Moved front tires to rear and it went away.
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yeah, I have visually inspected the tires, although they have a lot of time on them they dont have any buldges in them or excessive wear.

out - at

away.
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"its so loud you cant hear the radio at 60mph and it shakes like hell."
Are you still driving it like that?? Did you get any costs on wheel bearings for this vehicle? How can you tell if the wheel bearing is bad? I'm going to move the tires to the back just to rule that out first.
On a side note, sid you ever find the 4-button TCCM?
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This is totally true.

We only drive it to take trash to the dumpster less than 100 yards away, I havent put gas in it in over a month, its got cobwebs growing between the side view mirror and the windows.
Yes, the wheel bearing used around here I got priced at $75 a new one from autozone 169.99. The bearing comes in an assembly, and its the entire hub/bearing.

I am going to do the same.

No, no one has this part, and its 425 bucks new.
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"John Manner" wrote:

that
My guess is that the front axle is not disengaged because it will make some sound when engaged. Verify that it is fully disconnecting in 2wd mode. This is where my nickle is.
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I rotated the tires and verified that the front differential was disengaged. The noise is still there. I think it is the Transfer Case or the Wheel bearings. What do you guys think?
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John Manner wrote:

Not likely the Tcase bearing if it is fu;;y disengaging. Wheel bearings would be the next thing to check.
----------------- www.thesnoman.com
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: :: :::> Driving from 30mph to highway speeds I can hear a slight humming from : :: :::> the front end along with vibration sometimes in the floorboard. It : :: :::> isn't loud or anything, I just know it is there and that it is a new : :: :::> sound. After looking at posts for awhile, I have seen suggestions that : :: :::> the differential is engaged to bad wheel bearings. I can say that it is : :: :::> quiet at low speeds. What do you guys suggest I look at first? : :: :::> : :: :::> Thanks, : :: :::> John Manner : :: :::> 1999 Blazer 4.3L 4x4 (AutoTrac) : :: :::> 97,000 miles
This happened on my 98 Blazer, and driving into a strong wind really made it sing. Turned out to be the aluminum skid plate under the transfer case. It's mounted using shoulder bolts and spring washers that was worn out allowing the plate to viberate. I replaced the rusty spring washers with stiff rubber washers and the problem went away. This setup is supposed to let the plate move.
BTW, I have the ZR2 package and don't know if this skid plate is on all the trucks.
LockJaw
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I'm leaning away from the xfer case anyway because the noise is louder at speed and seems to be more pronouced (I think) on roads that curve to the right. So that would mean the left bearing is bad? I would replaced them both anyway but just checking. Speaking of that, how do you check to see if wheel bearings are bad?
I'll check the skid plate just in case, but I don't think my LT model even has them?
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John Manner wrote:

Jack up the truck and check for slop in wheel and how it feels whe you rotate it for starters. Also I have seen tire belts or tread wear cause noise too and you might swap tires front to rear and see if it moves
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