Humming noise/Ruling out bearing?

Ok so my 07 has been making a front end humming noise for about 10 months. The reason I have let it go so long is because it only presents itself when it is below 60 degrees outside. It only does it when the engine is around 1200-1500 rpm and as soon as you give it more gas or let off it disappears?? It is driving me insane and I cant figure out what it is. I replaced the passenger wheel bearing last year so I know what that sounds like. Im thinking maybe a motor mount?? Please help guys!

 

Does it not do it neutral and only in gear when you give it a tiny bit of gas????
Any possibility it could be coming from the rear??
I'm thinking the rear differential? Or possibly a U joint???

I'd check the Diff fluid /level for starters. Might be dirty r rend oil or pinion preload/???

 

I cant do it in neutral. Its def not coming through the rear. I had the diff fluid changed out on both diffs about a year ago so that should be good. It has me puzzled!

 

Does it not do it only when you give it a tiny bit of gas???? (very light acceleration - coasting no - very light acceleration yes ??

If So, Pull the rear drive shaft put it in 4 wheel drive and take a ride. If It's gone It's the rear diff. I had to have mine change at about 5K miles.

 

I've have something similar happing right now and was told its bearings in the front diff. or something like that. If that even makes sense....

 

Its definitely not a bearing for me because it happens as soon as I hit the gas from a stop. Only when I give it the right amount of gas though. Shit is driving me nuts!

 

It's four wheel drive right?

Take off the drive shafts one at a time and see if it goes away. When you remove the rear shaft just put it in 4x4.

 

Also, is your speedometer electronic?? Probably right?? I was just tinking on the older cars with a speedometer cable they just to get noisy sometimes.

and for a stretch ... leaking vacuum hose??

 

The sound also varies when going over bumps?? Motor mount?

 

Is It Possible the U joints have dried out and when the temp drops they start singing ??? This would fit a lot of the symptoms ...

 

mud boggers.

 

Idk man...had a 90 4runnner that did the same thing when it was below zero, only below zero?!?