97 Nissan PU 4x4 noise under vehicle

[willshak]

Screeching noise coming from under vehicle when driving. It varies in
pitch and loudness through the accelerating cycle but stops when vehicle
reaches ~50 mph. It will return when the speed drops below 50. The noise
remains when coasting with the clutch pushed in or when transmission is
in neutral.
I pulled the rear brake drums, but the pads are good and there is
nothing loose in there.

--

Bill
In Hamptonburgh, NY
In the original Orange County. Est. 1683
To email, remove the double zeroes after @

[Winston]

On 9/28/2010 7:35 AM, willshak wrote:
> Screeching noise coming from under vehicle when driving. It varies in pitch and loudness through the accelerating cycle but stops when vehicle reaches ~50 mph. It will return when the speed drops below 50. The noise remains when coasting with the clutch pushed in or when transmission is in neutral.
> I pulled the rear brake drums, but the pads are good and there is nothing loose in there.

Does the noise present after you un-mount the alternator/
water pump vee belt?

--Winston

--
Corporate executive forgets to commit a felony for 24 hours.
Film at 11.

[willshak]

Winston wrote the following:

> On 9/28/2010 7:35 AM, willshak wrote:
>> Screeching noise coming from under vehicle when driving. It varies in
>> pitch and loudness through the accelerating cycle but stops when
>> vehicle reaches ~50 mph. It will return when the speed drops below
>> 50. The noise remains when coasting with the clutch pushed in or when
>> transmission is in neutral.
>> I pulled the rear brake drums, but the pads are good and there is
>> nothing loose in there.
>
> Does the noise present after you un-mount the alternator/
> water pump vee belt?
>
> --Winston

It's not coming from under the hood.
The noise only happens when the truck is being driven, and it comes from
underneath.
As long as the drive train is turning, the noise is there, except it
seems to disappear when the truck reaches 50 MPH, but returns as the
speed decreases.

[willshak]

willshak wrote the following:

> Screeching noise coming from under vehicle when driving. It varies in
> pitch and loudness through the accelerating cycle but stops when
> vehicle reaches ~50 mph. It will return when the speed drops below 50.
> The noise remains when coasting with the clutch pushed in or when
> transmission is in neutral.
> I pulled the rear brake drums, but the pads are good and there is
> nothing loose in there.
>

I took the truck out for a test ride of about 1/2 mile today (down the
street and back).
The noise started as soon as I started to move, almost before the
speedometer started to move, and it is a rotational noise. The
rotational noise is also of a higher rpm than it would be with a wheel
turning (maybe 2-3x), so it is not a wheel bearing. I now believe that
it is the drive shaft center bearing.
I should have waited until after dark for the test drive. It was 75º F
out and there were a lot of neighbors outside. They heard me coming and
watched me go by. I was embarrassed.
This truck is 13 years old, but only has 78,000 miles on the odometer.
I'm taking it into the local mechanic tomorrow morning.

[Winston]

Oil level in the transfer case?

[willshak]

Winston wrote the following:

It's more of a high pitched noise, not the growling type of noise
affiliated with bad gears and bearings which are internally cased.
I have had this truck since new and there has never been any evidence of
any fluids ever having leaked from any parts. All parts that contain
fluids are clean and there has never been any evidence of any leakage on
the part of the driveway where I always park. This includes the
crankcase, manual transmission, differential, fuel tank, brake lines, or
radiator.
I suppose I will find out tomorrow.

[Winston]

Was the transfer case oil level correct during your last
15,000 mile change?

--Winston