I have a 2006 chevy silverado 4X4 that I bought 2 weeks ago in colorado, I drove it around chevked fluids and thought it was a good truck.

We drove the truck from colorado to new mexico with no trouble, until the next day we got home I started hearing a grinding sound from underneath the truck, my husband checkes on it nothing seemed loose we googled every possible reason came up with it could be the wheel bearings we replaced them no luck, a mechanic told us it could either be the t case or rear differential we decided to give it a shot we replaced the t case and that damn noise wont go away now i dont know what to do we checked the rear diff fluid and it looked clean and with enough fluid where is thia grinding sound coming from?? Its driving me nuts 4x4 works wonderful i dont think ( i hope) its the tranny this sound comes on whem driving in all gears I even put it in neutral to see if it was the tranny and step on the gas no sound, it only comes on when in movement, somebody help!!

 

Did your mechanic change the bearings and trans case for you w/o confirming the noise source? Some things to check include:
Can you tell if sound is coming from front or rear?
Does it change pitch with speed?
Can you feel it in steering wheel?
Does it change if turning?
Can you hear it with motor off, coasting down a hill in neutral?

 

My husband change d the bearinga and transfer case the mechanic onoy told us it could be those parts...

It does not sound when in neutral thr sound starts at 25 miles and up you can hear it with your windows down and as you keep accelerating the sound its steady

 

Just to clarify - if you are going above 25mph and the sound is present, if you put it in neutral does the sound persist?
Also, considering the money and time you have already spent, might I humbly recommend it may be a good investment to let a competent mechanic make a diagnosis for you?

 

A pitted pinion bearing and race could do it. You won't notice it at lower speed. There's a crush sleeve in there that's precisely set so don't just go messing with it without reading up on it good. Although, it wouldn't just be noisy one day and not the previous day.

Parking brakes? Are the parking brakes partially applied? They are ring shaped shoes behind the rear rotors. Maybe take a look there to see if one is broken.

Could be something rubbing on the drive shaft or front axle shafts.

I doubt it would be the trans. Different clutches are applied which spin different assemblies inside so the sound would most likely change or go way with shifts.

 

did you find a solution to this problem??? I have the same model truck and the same problem, I literally have the truck on jackstands right now with both rear axles off waiting for an answer since I see that my rear bearings don't look broken.