I would check the basics first, check the outer hub bearings and make sure there is fluid in the diff.
Any howling on/off throttle?
Lean on it hard in left/right turns, any difference in noise?
Is it RPM sensitive? Engine speed? Axle speed?
Any "clunk" from rear?
One of the problems with these is that there is no provision to drain the units, so they never get properly serviced, and there is no way to get a good low-point sample from them.
If the ring & pinion don't have a lot of perceptible lash, and there is no howling going on, it's probably OK.
If the R&P or carrier bearings fail, the gears will go out of mesh and it will make noise, and there may be excessive leakage from the pinion seal. This is where you can get in trouble because replacements will have to be set up for proper mesh and preload.
This procedure varies slightly depending on whether the unit has shimmed or collapsible spacer for preload, but it is a bit involved, although not terribly complicated if you understand it.
The differential gears themselves are a problem area, the thrust washers get beat to hell and the axle/spyder gears get a lot of lash, this will give you a clunk.
Driveshaft u-joint & balance issues are another source of harmonics.
The stub axle bearings are serviceable independent from the diff unit.
Outer hub wheel bearings, since you have replaced them already you know that's fairly straightforward, if you can get the wheel flange off (!), but the potential problem is with the inner needle bearing riding directly on the axle shaft/journal. Any pitting in the surface will eat the new bearings.
Try to narrow it down a little, it's most likely something you can sort out yourself.
If it turns out to be in the diff itself, you may have the option of building up your spare and then just doing a swap. A partial teardown will be necessary to do a proper inspection.
Glen
--Previous Message--
: With the oil pressure in the 1500 issue
: at a point where nothing more can be
: done I am planning on addressing other
: problems.
:
: When test driving the car after the
: engine went in I found it hit a
: horrible resonance at 50 MPH and made
: loud roaring noises from the rear. At
: lower speeds there is a definite speed
: dependent "whoosh, whoosh,
: whoosh" noise. I replaced wheel
: bearings a couple of years ago and
: would like to think that they have not
: worn out with the limited use my son
: has given the car. My suspicion is the
: differential.
:
: Can you suggests tests or things to
: listen for that would indicate a
: failing rear end?
:
: If it is the differential, I have a
: spare that came with a parts car but
: its condition is unknown. Reading
: Bentley, it sounds nearly impossible to
: rebuild one at home but perhaps some of
: the bearings can be replaced. Are
: there online resources that are
: better/simpler than Bentley that can
: walk me through a reconditioning
: process if not a full rebuild?
:
: I may not need to do anything but I am
: curious if this is an area that I
: really do have to leave for a pro.
:
: Doug L.
:
:
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