'98 V6 High Pitched Whine???

[skid marks]

Can someone please point me in the right direction... I am good with cars and trucks, but i cant figure out where to start with this whine i am getting.

Symptoms...
High pitched, sounds almost like a "hub" isnt locked in all the way.
Sounds like it might be coming from the drivers front when driving
Sounds like its coming from the rear axle when in the back seat
Becomes obvious around 30 MPH. Loud around 50.
If i let my foot off the gas it gets quiter, but still there.
Applying the gas above 30 makes it louder.
Putting it in Neutral also makes it quiter.
While in Neutral the truck coasts perfectly fine and the whine is not overly noticeable.
Transmission seems to be shifting perfect.

I just had my transfer case replaced about 2 months ago.

Any help would be greatly appreciated...

 

[my98nnj]

Did the wine start after the T-Case was replaced?
Was it a new, rebuild or a used t-case?

 

[skid marks]

I paid a garage to put a new one in. Might have been a rebuild. Was $1200 without labor. I guess it was probably a month after it was replaced that it started. I had to replace the 4X4 motor on the case about a month after as well. I made sure the fluid was full in it when i did that. One of the sensors was leaking after i got it back from the shop. The sound has gotten progressively worse over the past few months. My teenage daughter is driving it now so i am concerned that its going to finally give out when shes on the road.

I called the shop that installed it and told me it was most likely the rear axle. From the description of the whine getts louder and softer with the gas peddal. SO i am going outside now to check the fluid level in it.

Thanks...

 

[skid marks]

OK STUPID QUESTION...

The rear axle appears to be sealed. I can not find the plug to check the level. Only thing there besides the bolts holding the pumpkin cover on is a sensor (speed?) top drivers side. Believe if i do have a plug it should be right under the speed sensor.

Gasket on the pumpkin cover looks like it has been leaking for some time at the bottom. Don't tell me the fords "lubricated for life" rear axle dosen't has a fill plug???

If thats the case i will make one in the pumkin cover tomorrow.

But back to the noise... Is the rear axle a possibility for the description i have given?

 

[RomeovilleIL]

Fill plug is on the drivers side, front of the diff just above the centerline. It has a 3/8" square inset socket head. You can simply use a 3/8" socket extender as a driver to remove it. You should have oil up to the level of the plug. The case holds 3-1/2 quarts. There are a number of good threads on the site along with a couple videos on ehow which show you step by step how to replace the gasket if that's all which is leaking.

 

[1st explorer]

frt diff pinion

 

[OneLever]

Gasket on the pumpkin cover looks like it has been leaking for some time at the bottom.
...Is the rear axle a possibility for the description i have given?

Yes oil starved gears will start making noise. If you lost enough from the rear differential I wouldn't be surprised if that's causing the noise. Doesn't rule out the transfer case, but given that info I'd look at the differential.

 

[fatvdub]

Can someone please point me in the right direction... I am good with cars and trucks, but i cant figure out where to start with this whine i am getting.

Symptoms...
High pitched, sounds almost like a "hub" isnt locked in all the way.
Sounds like it might be coming from the drivers front when driving
Sounds like its coming from the rear axle when in the back seat
Becomes obvious around 30 MPH. Loud around 50.
If i let my foot off the gas it gets quiter, but still there.
Applying the gas above 30 makes it louder.
Putting it in Neutral also makes it quiter.
While in Neutral the truck coasts perfectly fine and the whine is not overly noticeable.
Transmission seems to be shifting perfect.

I just had my transfer case replaced about 2 months ago.

Any help would be greatly appreciated...

sounds like mine is making the same kinda noise