Front 4wd noise under acceleration

[sealandsky]

I'm curious as to how often you are driving around in 4 auto mode? And for that matter - under what conditions are you driving in 4H?

 

[the highlander]

Changing the shaft worked...

 

[BlaineBug]

Mine makes a distinct deep noise under load as well when in Auto or 4-Part Time. I too changed fluids early just as preventative measure. I'm not sure if it's front differential or transfer case related, but I am not concerned.