State of the Whine (1 Viewer)

[GatorPlater]

there are many threads about whine under power and I have read most of them and done the PM to hopefully fix.
Symptom: Whine/subtle vibration at speeds between 45 and 65ish, only under load, gas off, no noise.
What I have done so far:

1. Rebuilt front end, including replacing spindle bushings with 100 series roller bearing bushings (noise still there)

2. Changed all fluids in all 3 units (noise still there)

3. Installed new U-joints in rear drive shaft,Had it balanced,reinstalled, installed CDL switch, removed front Drive shaft, (noise is gone)

4. Installed new U-Joints in front Drive Shaft, had it balanced, re-installed (Noise is BACK)

So, I do not have access to electronic ears and the closest good cruiser shop is AAC in Atlanta(Will is awesome BTW). no one here in Jax works on them specifically that I can find.
The 3rd looks like it was rebuilt at some point as it has red RTV all the way around it in the seams.
Would it be a bearing in the Center diff as there is no whine with FDS disconnected, or a bearing in the front diff?
would it be cheaper to just buy a new front diff unit or have the current rebuilt?
swap out the center diff with a used unit or have it rebuilt?
Anyone?... Bueller?

 

[l0uciph3r]

My whine was due to the front diff - I had it rebuilt with beefier components, but a new one from CDan was about the same price - roughly 1K - afterwards though, no whine or vibrations.