When we returned home from our holiday trip I had #1 son test drive the Spitfire for his comments on the noises. His condensed reply is/was "Yes, it's loud. It's always been loud. Yes, it's made that noise for a while now".
In answer to some of Glen's points and comments...
The "whoosh, whoosh, whoosh" is road speed dependent and you don't notice it until going over about 30 MPH.
The resonance at 50 MPH is while under load. Take your foot off the throttle and the noise goes away.
Since the whoosh noise needs you to be going 30 MPH it was not practical to throw the car left or right to hear how turns affected the sound.
There are no clunks from the rear end either getting on or off power.
I will check fluids and some of the other suggestions on a non-holiday weekend.
Will I be able to "feel" bearing issues with the axle shafts if I disconnect the inboard flanges from the diff and spin the road wheel by hand?
I will inquire about driveshaft balancing. It may pay for me to have that done "just because". I know I put a u-joint in one end of the driveshaft but I have no idea if previous owners did the same without regard for orientation of the parts.
My thought at this point is to carry out a few of the external examinations of the diff I have and as Glen suggested, take the spare one apart for examination and possible rebuild. I told my son that if all goes well he may be able to take the car back to campus after Christmas.
Doug L.
--Previous Message--
: Well just a few random thoughts, others
: may add to it.
: 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
:
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