Diagnosing mysterious sound from Tran/Tcase

[nmcgowan80]

I'm just suggesting to shim the pinion up a few degrees and see what happens.

Yes, the angles are "supposed" to match. But, due to other variables, that sometimes doesn't work for the application. Not matching angles do not always cause a vibration.

I definitely appreciate the suggestion and I may try that.
When I bought and installed the 6" rear leaf kit from Skyjacker, there were angle shims already installed on the new leafs. At the time I just assumed it was a necessary part of the package and installed them accordingly. After installing them, my pinion angle was then pointed up directly at the transfer case. That's when the vibration started- when I started this rabbit hole of learned about pinion angles. I've since learned that having the pinion angle pointed up in that direction is required for a double cardan setup- not the single cardan setup I have. So I removed the shims and brought the angles back parallel (as indicated in everything I read). Vibration still there. So I dropped the transfercase with 1 inch spacers. Vibration still there. Goes without saying how frustrating it's becoming.
I'm considering traction bars . I've read that they reduce axle wrap. The skyjacker spings I have are "softride" and the vibrations mainly happen under torque and at freeway speed.
But you're right- I would think there are plenty of lifted squarebodies doing just fine without fancy double cardan rears or traction bars.
*sigh*

 

[nmcgowan80]

Here is what I have for reference

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[chief_shotts]

The front/rear shaft and U joints were replaced a year ago. Less than 1000 miles on them. I removed the rear shaft and tried to run with just the front shaft to narrow the problem down but for some reason I can't engage the transfer case to lock the front tires. But that's a different problem. When I bought the truck a year ago, it was squatted with a 6" up front and a 3" in the back. The driveline was installed at a shop with that setup. I installed 6" skyjacker leafs in the rear to level it out (and make it look better) and I'm 90% certain that's when the vibration started. I've exhausted myself reading up about pinion angles/operating angles etc. so I know that the rear pinion angle needs to match/parallel the transfercase angle in a single cardan setup which I've done with the digital angle finder. Still hasn't fixed the vibration at highway speed. So my options are:

1. take newly built driveshaft in for balancing (seems redundant)
2. replace newly installed u-joints (seems redundant)
3. get tires aligned/balanced (recently done)
4. replace driveshaft with double cardan and shim the pinion to point at the transfer case (not entirely sure if that's necessary yet?)
5. consider pinion bearings or transfercase yoke? (wasn't really an issue before the rear lift was installed)

I'm sure I'm missing some other things which is why I'm here looking for guidance/suggestions before I start throwing time/money I don't have at problems that don't exist. It seems like these vibrations are common but all the threads I've read here have had different solutions.

I solved my issue by ultimately adjusting the rear pinion angle up more. I shimmed it more than I thought was necessary based on the math a I did, but it worked so I'm not conplaining. I can now go very fast and it's a smooth ride.

 

[bucket]

I solved my issue by ultimately adjusting the rear pinion angle up more. I shimmed it more than I thought was necessary based on the math a I did, but it worked so I'm not conplaining. I can now go very fast and it's a smooth ride.

This is what I've been saying here already. Sometimes the "correct" by the book driveline angle is not the correct angle in the real world. Your truck is a perfect example of that.