Rear diff bad but noise in front?

HI everyone. I am new around here and I seem to be having an annoying problem. Here are some stats on my truck that can hopefully help diagnose what is going on:

2007 Chevy avalanche LTZ
169k miles on chassi
2,000 miles on transmission
800 miles on rebuilt motor


PROBLEM:
-Growling / whirling / grinding noise coming from what sounds like underneath the driver seat / front of the truck wile inside.
-Noise kinda goes away if I am doing 60mph and lift off the throttle or find the "sweet spot" with my throttle
-Noise is constant from 10mph and gets louder the faster you go.


PARTS I CHANGED SO FAR:
- Both front wheel bearings with Timken bearings
- 4 wheel pads and rotors from the factory


DIAGNOSTICS I'VE TRIED:
-Put vehicle up on the lift and the noise sounds like it is coming from inside the rear diff
- Driving the noise sounds like its coming from  under where the drivers feet are / Front diff area
- Rear diff noise happens in both 2wd and 4wd mode on the lift
- Noise under the driver side / front diff happens in both 2wd and 4wd mode while driving
-While driving I have put the truck in Neutral and the noise stays the same
-Grabbed the U-joints while on the lift and they felt normal / no play


Before I start throwing bearings in the rear diff only to find out its the front diff or transfer case what do you guys recommend I check? The noise is driving me nuts. It sounds just like a wheel bearing / front diff inside the truck wile its on the ground but then the rear diff while off the ground 

  Drain the diffs and T-case. Pull rear diff cover.
look for metal.

Go YouTube search Chevy 1500 T-case leak if you do
not get much oil out of it. Mine had no signs until
the noise came.


If all else fails have a shop look at. Then decide if you want to take it on.
Not throwing parts at it.

JVZL1 said:

  Drain the diffs and T-case. Pull rear diff cover.
look for metal.

Go YouTube search Chevy 1500 T-case leak if you do
not get much oil out of it. Mine had no signs until
the noise came.


If all else fails have a shop look at. Then decide if you want to take it on.
Not throwing parts at it.

Click to expand...

Ya, that seems to be the only logical decision left. Going to grab some diff oil and just pull it all down... if its not bad at least I changed the fluids

Remember to make sure you remove the front diff upper fill plug first, then remove the lower drain plug and check the magnetic plug for shavings.

Not being able to get that fill plug out makes for an interesting day.

Been there done that....that being said. Have fun
There is a web site and of course I can't remember what it is that tells you to a point what's the problem. Deep breaths and several members here will give you ideas. Also have someone else drive while you climb around the cab looking for the noise.
That being said pinion bearing.
Or parking brake.....