Well, an update and THE FIX! I thought I'd update this so anyone searching for vibe threads may come across it & fix their ODD issue. I've never heard of this one before.
As you can read above, I tried just about everything I could think of to chase down this vibe. I've been driving around at 40mph for 10 months, hoping somebody would have the answer. I've spent hundreds of dollars and countless hours troubleshooting this damn thing.
Drumroll please..........
The spring from the pinion seal had fallen off during the re-assembly of my differential (during the regear) and was smashed between the pinion gear and the yoke. :doh:
If you look above, you can see where I took a video of my driveshaft spinning while my XJ was on jackstands. That wobble floored me - even though a shitload of people told me it was an optical illusion. :bs:
I managed to take some flat stock, magnets and a micrometer this weekend and measured a .008" oscillation (?) of the yoke. I thought maybe the yoke was bent during installation or something. So, I decided to pull it off and put a new one on - and replace the seal. What did I find? See below. The pinion seal spring (round spring that holds the shape of the seal around the yoke) was 50% stuck in the pinion gear splines and 50% smashed between the yoke and the mating service. Luckily, I was able to dig out the entire spring!
I immediately took it out on a high-speed run (4.56s and 31s). It runs like a raped ape and will cruise at 75mph SMOOTH AS GLASS. No drones, no vibrations, etc. I've driven it 100 miles since & it is awesome.
Anyone seen this before?
