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Dry bearing roar noise eludes detection?

Ecomike

NAXJA# 2091
NAXJA Member
Location
MilkyWay Galaxy
87, Wagoneer, 4 WD, AW4, NP242, Dana 44 and Dana 30.

Been hunting for the source of a slow speed (1-2 second cycle frequency) dry sounding bearing roar noise that is never there 99% of the time, making it impossible (so far) to find the source.

It sounds like what a dry worn wheel bearing would sound like at low speeds.

That said, I only hear it at 3/4 WOT, between 10-20 mph in second gear, in 2WD mode (Have not tested for the noise in 4WD mode).

At 0-10 mph, from a coasting speed to 1/2 WOT and at WOT, no noise, and above 20-25 mph, up to 70 mph, in all gears, from coasting to WOT I can not hear it at all (maybe too much other noise).

I would think a bad wheel bearing or real bad U-joint would get louder as the speed increases (based on my experience).

I have inspected the front and rear drive shafts, and they are in great shape.

I jacked up the rear and ran it from 0-50 MPH at idle to maybe 30% of WOT, and could not hear the noise at all.

Jacked up the front and manually spun the tires, and it sounds fine there.

The front and rear brakes, rotors, drums, pads, MC, Brakebooster, 100% new and working perfectly.

I can take it up to 30 mph let my foot off the gas and coast for maybe 3 minutes before gravity stops forward motion, so it does not seem to be wheel bearings or brakes.

I discovered the noise 3 months ago, and it was two noises. One noise was loose wheel nuts from the brake work 3 months ago. Fixed that noise, and the wheel nuts have been checked 3 times since they, and they are staying on fine, but this other noise lingers.

T Case fluid was a little low (leaks), and I topped it off this weekend, but that made no difference in noise, or other normal sounds.

I don't think it is engine related, as I only hear it under load, at 3/4 WOT in second gear at about 15 MPH. AW4 is working perfectly.

I have inspected and felt the Dana 30 from drive shaft U-Joints and they look and feel solid.

Any ideas NAXJA????
 
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Oh, and this a 100% stock jeep!
 
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