4406 swap vibrations

[EMG7895]

Anybody else having issues with front shaft vibrations after a 4406 swap? My stock height, stock tire size mounty makes a loud "roaring" sound at highway speeds along with a vibration. Only occurs with the front double cardan shaft installed. I had the shaft balanced and that made it better but it did not fix it. I found a few other threads here mentioning pinion angles but none with a resolution.

 

[EMG7895]

Some interesting things I have observed is that the vibration get worse when coasting/ decelerating, and also the vibration is pretty much gone when in 4 hi. Any ideas?

 

[boominXplorer]

I had horrible vibrations with mine but it was because of the 5" rcd lift. It aimed the pinion way to far up. I just rode with no shaft till I went wheeling.

Edit: I take it you have a 97 which is stock double cardon. Did you change the u-joints since the driveline angles have chaged?

 

[EMG7895]

Its actually a 99, got the shafts from another member on here. No lift so pinion angles are stock, all of the rear u joints are new, as well as the front conversion joint. The shop that balanced it said the two double cardan joints were fine so I haven't replaced those yet.

 

[EMG7895]

I was previously mistaken, as the vibration still exists without the front shaft, although maybe not a bad. I'm going to have the rear shaft balanced and hope for the best.

 

[EMG7895]

Update: With both shafts balanced the vibration is gone, but returns intermittently. It will drive smoothly at highway speed until I slow down. Canceling cruise control without my foot on the gas immediately results in a strong vibration. I can stop the vibration completely by momentarily shifting into 4 Hi, and it will stay smooth until I slow down again. Could it be possible that the double cardan joint is worn ?