Need Help Troubleshooting A Front Hum

grimmysnr · November 22, 2008

For those who havnt read my posts before I have an 06 Sierra that I was very mean to when I first got it. As in taking it out in the Alaskan wilderness and 4 wheeling through stuff some trucks are specially built for. I have had the front end airborne going over bumps a little too fast and trying to cross a few rivers which brought water up over the hood. Anyway...I have had the front diff rebuilt with new carrier bearings, gears, output shaft seals etc. I have also had the intermediate shaft replaced. I have pretty much replaced all the stuff that I broke and been taking good care of her since. However, the stuff I went through before contained a lot of glacial silt which is a very very fine type of sand that can find its way into any crevice possible on a vehicle. Which leads me to believe I have had this silt grinding its way through my wheel bearings for a while. As in 40k miles and 3 years.

So as for the noise, its not a constant hum its more like a wave of hums. Happens about 25-75+ MPH on straight flat and level driving. The humming goes away while turning in either direction but I believe thats because I am too slow to create the noise. For example I dont necessarily take turns going 50 MPH because thats kinda unsafe. But if I am going about 20ish and above (its the loudest at about 35mph) and I go around a curve or something the noise will remain. It happens in 2 and 4 wheel and I do have BFG All-Terrains but I am confident its not road noise since the noise is persistent on snow and ice. I have had the front end on jacks while changing the oil and no noticeable wheel movement was witnessed.

The noise isnt a front diff growl or roar it is just a light hum that can be heard when the radio is off and faintly felt throughout the stearing wheel and floor board. The hum isnt a hummmmmmmmmmmmmmmmm etc etc thats constant. This hum is a hum...hum...hum..hum and increases in frequency with speed.

Any input? I am still under warranty so I was going to take it in but wasnt sure if its a covered item. I am a mechanic by trade so I have some troubleshooting experience under my belt. If its something cheap to replace then I have no problems doing it as most of the stuff I have replaced I have done myself. But if cost is an issue I might as well have our frugal friends at General Motors pay for it.

Thanks guys!

Jason