The howling wont stop

[vidfix55]

Ok i need some major insight on what to do next. I have a 1999 explorer limited 5.0 with awd. I bought it from a friend who just had the transmission rebuild for a shifting issue. When i bought it, it always has this howling sound like wheel bearings going out. My friend said it always has done that and he was unable to locate the issue for years. He though the transmission rebuild might fix it but it did not. So ive been trying to fix the issue. This is what i have done. Front wheel bearings (actually twice to make sure i didn't get a bad set), tires (yes they are all the same size) , rear wheel bearings, front and rear carrier bearings, front pinion bearings, front intermediate shaft bearing (basically rebuilt the whole dana 35 sla front end). New cv axles, new u joints. Still howls and the howling goes with the speed of the vehicle it starts about 20mph and goes from there but you can still hear it a lower speeds. If im on a dirt road i can hear it. Its definitely towards the front. I've disconnected the front drive shaft, still does it. If i jack it up all 4 off the ground, it goes away. Its not load dependent, its only speed dependent. Putting it in neutral and rolling you can still hear it howl. I cant imagine what else it would be except possibly output shaft bearing? Ive heard bad transfer cases before, they sound more like a wirl sound and go away when the load is off. Any one else have any idea? Basically the whole drive line is new at this point

 

[410Fortune]

this is not your typical transfer case it is AWD and uses a viscous clutch
However the t case noise usually goes away when you disco the front d shaft

the only thing left is the rear axle or torque converter\
Assuming the TC was replaced with the rebuilt 4r70w trans.....I would start to suspect the rear axle pinion OR the AWD t case is really messed up
You said you can still hear it when rolling in Neutral.....



How many miles on this explorer?

 

[donalds]

The dreaded pinion bearings
Hope not tho but not such a bad job if you have some muscle

 

[vidfix55]

The front pinion bearings are new. Vehicle has 250,000 miles on it (just barely broke in). Under it this morning i saw that i have a front output shaft seal leak.

 

[donalds]

When my rear pinion bearings went south the noise bounced around everywhere I had to put it on Jack stands then put it in gear I then used a piece of plastic hose like a stethoscope at no point did I get under the truck while it was in gear has my son in the driver seat found it was loudest at the rear pinion hope yours is not