So
early this morning I followed your guy's advice and flipped the TRX-4 on her back and from there loaded the rear and front drive-line independently. Video below shows the results:
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You should be able to see that the rear (furthest from the camera) did not cause a squeak, while the front did.
Then, for some reason, after determining the
FRONT drive-line was the problem, I decided to take the
REAR drive-line apart....did I mention it was early and no coffee yet?
Surprisingly (
sarcasm) when I loaded just the rear drive shaft, I heard no squeak. I then proceeded to disassemble the rear axle/diff/portals, re-grease, re-assemble, and put it all back together to come to the realization that I was working on the wrong part of the drive-line....sigh.
Now, on to the front. There I was able to load just the driveshaft and found that the end on the transmission was squeaking, so I swapped the shaft around to see if the squeak followed the driveshaft or stayed at the transmission. It followed the driveshaft. So I took both driveshafts out, for good measure, and disassembled them. I found some rust, which I cleaned out, worked the joints around a bit, then put it all back together,
squeak is gone! (for now)