Chasing Vibration -
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Unread 09-02-2008, 10:31 PM   #1
Registered User
1992 YJ Wrangler 
Join Date: Oct 2007
Location: CA
Posts: 94
Chasing Vibration

I been helping a friend track down a vibration issue on his Jeep, and now we are looking for some input.
Symptom- Vibration between 30-40 MPH
Setup- 8.8, flat springs, SYE/CV(hack n tap) drive shaft,4.0, manual.
Background: A couple months back he discovered a large crack in the bellhousing. After replacement the vibration started. I assumed that the vibration had always been there, but not noticed because the broken bellhousing compensated for the movement, and the vibration caused the bell to fail in the first place. Our first suspect was the pinion angle. The rear was not setup very well by the previous owner. I cut the perches off and set the pinion just like all the write-ups said to do. (Same setup works great on my Jeep) Motor mounts and transmission mounts are good.

Now for the good stuff: Having eliminated all the normal stuff we raised the rear of the Jeep and ran it through the gears. We noticed that the CV was not soaking up the movement, and the output flange of the T-case was wobbling. The CV it self seems to be in good shape, so we removed the drive shaft and watched the output. With the drive shaft removed, the output flange is still quite wobbly. I didn't measure it, but it is quite visible.

Question time:
Is it normal for the Hac-N-Tap to wobble?
Could the splines be worn?
The output shaft itself does not seem to have too much play, but I wondering if it could be bent.

Any ideas and or suggestions would be greatly appreciated.

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