Slight vibrating at 10 mph

I recently installed some 5100's, 887 springs and dakars. Also 285 75 16. I also had the alignment done. All is fine but I have a little vibration at low speeds. I notice it most at 10mph and seems to go away then maybe barely at 25 then gone. Thought it could be the tired at first (big tread) but it seems to be when I press the gas.
I am aware of the needle bearing issue. I have no noise and upon inspection, I can move the cv in and out slightly but it is rock solid up/down, left/right. It seems to be from the rear. I DO have the included carrier bearing shims from Headstrong. Could it be I need bigger shims? Hopefully it's nothing in the rear diff but I doubt it. Any ideas? I'm wondering if I should load the back with some weight and see if it goes away.

 

Put in 4Hi let us know if it goes away

 

Yeah I did see that mentioned. I'll try it tomorrow for sure. Thanks dude

 

If the sound goes away in 4 high, does that usually indicate a needle bearing failure up front due to lift?

 

Oh, you're gonna hear it for this one! LMAO

 

Affirmative

 

I get this too, same set up but stock tires. It's only when slowing down.

 

Tested in 4wh and same vibration. On a side note, when engaging and disengaging, there's a pretty audible click. Not trying to be a pansy but is that normal? I'm thinking the vibration must be something with the driveshaft. I'm going to measure the angle.

 

Perfectly normal, and very annoying. You'll get several clicks, clunks & grinding if it has a hard time selecting 4hi or 4lo.

 

The way a 2-piece driveshaft works...you don't want a carrier drop on it.

 

I have the shims provided in the kit. Are you saying I should not use them? Not sure I follow.

 

You can't equalize a driveshaft with 3 joints...needs an even number.
If you suspect angles, I'd take out the carrier drop and just worry about the center and rear u-joint.
The front shaft needs to be as straight and inline with the engine/transmission/transfercase as possible.