Dang, Tony. It is a shame we live so far from each other. Otherwise I would be offering to come over, or have you come out to our place, so I could hook up my Chassis Ear equipment and find out precisely what is causing the noise, It is easy to do, and the equipment is not that costly,. The equipment is available in two flavors, wired or wireless. Of the wireless version there is a Bluetooth and a UHF subversion. I have not heard much about the bluetooth wireless system, but the UHF version not only gets rave reviews, but I have personally used it to verify a bad wheel bearing, and have even used it to perform diagnostic work on my old pony cars.
Their wired version is fairly inexpensive. Their wireless system is a bit more, but you won't have a lot of long wires to secure under the car so you can go out for a test/diagnostic drive while listening to the various clamp-on "microphones" while you are going down the road.
Here is the web site where you can order your kit from the manufacturer.
https://steelmantools.com/collections/noise-vibration
For the record, I have used both the wired and the wireless units. They both work extremely well. But with the wireless unit I do not have to deal with nearly 20 feet of wire being held in place using Zip Ties and/or Velcro straps. With the wireless system there are clamp-on microphones also, with cabling. But, the cabling is just long wnough to connect to a radio signal transmitter that gets mounted near the clap-on microphone. I recently diagnosed a set of failing wheel bearings for a lady who was told she needed new wheel bearings. She did not hear any noise from her front end, nor did a mechanic she brought the car to for the purpose of verifying the problem. The other day I hooked up only two wireless transmitters with their respective clamp-on microphones. Wow, the Chassis Ear made it very clear that she definitely had a problem, despite it was not loud enough to be noticed in person.
Anyway, I got our Chassis Ear kits on a lark, thinking I could likely use them someday. After seeing how easy the equipment is to set up and use I can assure you I am going to be using the bee-geebies out of it. I have both the wired system (
Part #: 06606), and the wireless (
Part #: 61082) system. Highly recommended. In your case I would attach one clamp to the rear axle housing where the pinion shaft is located. I would put another on the rear axle housing, and the other two I would connect to the axle housing near rear axle bearing. If none of those locations are creating the sound I would attach one of the clampon microphones to the tranny tailshaft housing and see it that bushing has worn.
I should clarify what I mean by a clamp-on microphone. The sound sensors and not anything like a conventional microphone. They are heavy duty spring loaded electrical (like car battery charger) clamps that are equipped with a vibration/sound sensing Piezo Chip. Then a wire runs either to the wired kits control box where you can select up to 6 such microphones. For the wireless unit there is a short wire connection the "microphone" to a wireless transmitter, and finally a wireless receiver gets the waveform file(s) needed and then the diagnostic process is done - and quickly.
If you are interested in how well the Chassis Ear works I have taken recording of the wheel bearing on my friend's Toyota, then put a sample of the vibrations captured by Chassis Ear in comparison to another vehicle with one good wheel bearing set, and the second car that just began to make funny noises, to make noise. The audio file has four parts., The first is a Toyota with a wheel bearing that is just beginning to make noise, The 2nd part plays the loud sounds of her driver side wheel bearing set. The 3rd part is the good bearing on the Toyota. The 4th part is another (passenger side_ wheel bearing that is obviously dry and in the early staged of failure. Bear in mind, with the sounds I captured none of them was detectable without this equipment.
https://drive.google.com/file/d/1rHkQ7p86pZroNYAmTnyJVGB2LjCHBAIw/view?usp=drive_link
I bet once you use this solution you will be singing its praises.