Driveline is Whining

[zaidtoronto]

I Have a consistent whining noise from 55mph to 60mph. I have noticed it rumbles around 25mph, turns into a whine under acceleration at 45-60mph. Then above 65mph the engine pretty much drones out the sound. it also whines when slowing down (when the injector cackle noise is not present) replaced carrier bearing, noise still there.
it all happened after transmission oil change. then i did another complete oil change and filter with mobile 1 to see if the noise going to go away but still the same. any help? thanks, Zaid
and yes it is 1999 ford F450 with a 20ft box used as a moving truck

[ttyR2]

From my understanding, if it's an issue with the rear differential, the pinion bearing will go quiet when you let off the pedal (because the hypoid gear shape will pull the pinion backwards taking pressure off the bearings). If the whine stays there, then it's probably the ring/pinion as they will make the whine noise constantly once going faster than a given speed.

[zaidtoronto]

Originally Posted by ttyR2

From my understanding, if it's an issue with the rear differential, the pinion bearing will go quiet when you let off the pedal (because the hypoid gear shape will pull the pinion backwards taking pressure off the bearings). If the whine stays there, then it's probably the ring/pinion as they will make the whine noise constantly once going faster than a given speed.

is it so critical if i just keep driving it this way? the whining actually happens when i slow down at low speed with foot off the pedal