growling noise on de-accel

[OrangeF150]

I had a slight hum while driving around and faint "grrrr" sound coming from the front end only when you de-accel (let off the gas) You can kinda feel it in the steering wheel and seat. I just replaced the wheel bearings with some Timken ones and noticed my driver side half shaft seal is leaking, there is still plenty of fluid in the diff though.Could this noise be the half shafts? I think the passenger one had some slack in it wen I held it still at the diff and turned the hubb back and forth.The hum is now gone, but it still growls when letting off the gas.And when it does it, I even tried putting it in Neutral and its still there.

Vehicle BTW is a 01 ST 4X4..Thanks

 

[BrooklynBay]

Put it up on a lift, and listen underneath. Try to locate where the noise is coming from while the wheels are turning slowly .