Rear diff howl?

Hi everyone,
ive been searching the forum for some info about a new howling noise I'm getting in my 2015 Tacoma. It's 2wd 4 cyl. Before I call up the dealership I want to get as much info as I can. it's a subtle howl around 2000 rpm while feathering the gas pedal, engine under load. Happens regardless of speed. Doesn't do it in neutral (no load). The problem is from the drivers seat it's hard to tell where the source is. Sometimes it sounds like drivers side engine compartment? Truck has 7500 miles. The only thing new I've done recently is put 300 lbs of sand in the bed for winter..has anyone else had this problem with 2wd tacomas with access cab? Thanks in advance for the help..

 

sounds like a bearing... only question is which one. If it only occurs when eng is under load could be carrier bearing or pinion bearing... noises are hard/impossible to diag over the interweb

 

sure you don't have a 2016? I would check or change out the rear diff fluid. also most all vehicles will have driveline/road and tire noises that are misconstrued as problematic or a catastrophy looking to happen. grease the universal joints also they come ungreased from the factory

 

Thanks for the quick replies. Just checked and none of the u-joints are serviceable, no zerks. I'll check diff fluid after work...going to try and get audio recording of the howl also