97 Nissan PU 4x4 noise under vehicle

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.

Reply to
willshak
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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.

loose in there.

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

--Winston

Reply to
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.

Reply to
willshak

willshak wrote the following:

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.

Reply to
willshak

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.

loose in there.

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

there were a lot of neighbors outside. They heard me coming and watched me go by. I was embarrassed.

Oil level in the transfer case?

--Winston

Reply to
Winston

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.

Reply to
willshak

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.

loose in there.

street and back).

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

and there were a lot of neighbors outside. They heard me coming and watched me go by. I was embarrassed.

with bad gears and bearings which are internally cased.

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

Was the transfer case oil level correct during your last

15,000 mile change?

--Winston

Reply to
Winston

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