I have a '99 E150 that I use for work. about 18 mos. ago it developed a rear end shimmy (right rear) and my mechanic found that the axle shaft and bearing were worn so he replaced it. recently I am hearing a humming in the same location but no shimmy. before I bring it in again I wanted to get an opinion though. also the noise happens only between 35 to 45 mph with your foot on the gas. in other words, if I coast at that speed the noise drops off. Fluid was about 1/3rd bottle low when I checked so I topped it off.
Thanks

 

Did you take a lube sample?

Any 'suspended' metals in the lube? (metallic looking lube) or debis stuck to the drain plug..

Usually a noise that 'quites' when backing off of the throttle is gearset related. Sometimes it will increase when harder throttle loads are applied, but generally has a more 'annoying' zone. Depending on how the set is worn, will determine noise if the 'growl' or whine ect is on deceleration, or accelleration.

Higher pitch noises, tipping the throttle IN/OUT, tend to be pinion issues.

Axle noises are usually easily produced/re produced just by 'rocking' or transfering the vehicle weight from 'side to side' when driving using the steering wheel to transfer weights.

Constant or consistant rumbling usually is gearset carrier bearings, but can be axle noises as well. But, if making side to side weight tranfers changes quites the rumble, then axle bearings/axle would be suspect.

High pitch chirping tends to be u-joint related..

 

thanks for the info. there is no drain plug so I have not taken a sample. I can clarify the noise a little. there is no whine but it makes a howling sound like you would hear when air rushes through an hollow pipe