My 2001 Blazer S10 4wd has a stupid loud roar when going 70mph and quiets down to unnoticeable levels around 78mph. Its loud enough to need ear plugs at times. It stops when I turn the wheel to the right but not to the left. Sounds like its coming from the driver side gear assembly but I've replaced that and it didnt fix it. Any idea? There isnt any vibration and most of the posts say vibration.

 

Gear assembly? Is that the wheel bearing assembly? I am thinking bearing noise, mine was pretty loud before I changed both front wheel bearing assemblies. Turns out only one was bad. Pretty easy job.
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Sorry that I'd what I meant. I've replaced the left hub assembly since that is where the noise is coming from but it didnt stop.

 

New or used? Proper torque? Did you check your cv axle? Dumb question but how are the brake pads? Could be the warning strip...

 

I replaced it brand new to the factory spec torque. Funny enough i was messing around with it and found that my 4wd will not engage. So that might have something to do with it. I get flashing lights but no solid and it reverts back to 2w Hi. So I hope it isnt the transfer case.

 

Check out your tires and maybe rotate tires front to back and see if noise transfers with the tire rotation - a tire starting too separate will give you the same type of noise your experiencing .....

 

I have a question; on the old bearing unit that you took off. If you hold it in you hand and press on the hub could you feel rough bearings? I have been curious in past working on other cars as to why they were making noise and found that the race was chipped and coming apart. Took torch and cut it open. Is it possible that the other assembly is the problem? On my Blazer, I replaced both at the same time. One was really bad and they had been changed out before I purchased it.