Help ID loud pop and shutter when flexing rear axle

When I flex the trucks suspension, there is a really loud POP from the rear end somewhere. When it happens, the entire truck jolts. I have no clue what it is

specs:
Wheelers 5 leaf spring pack
Bilstien 5100 socks
new shackles

https://www.youtube.com/watch?v=ySnew42SsAQ

 

anyone have a clue?

 

I'm thinking that a moving part is coming in contact with a non-moving part while flexing, causing the noise. If so, you should be able to go under there carefully inspect where all the new parts are, and see a sign of wear (shiny metal rather than dirt and rust).

 

I definitely will check that out when I can get to my truck towards the end of this week, although I did get out when parked on the hill and look underneath quickly. I didn't notice anything

 

What leaf springs are you running?

 

Wheelers 5 leaf pack, as stated in the op

 

Check the outer axle bearings.

 

Another thing i would check would be to make sure the springs arent making contact with you shocks when its flexing or at full compression. Not sure if your running blocks in the back but blocks tend to amplify this problem. Just a quick check you can eliminate. The other thing i was thinking was your slip yoke but iv never heard of one making a bang like that.

 

regrease slip yoke on the driveshaft....I don't mean with a grease gun either, drop center support bearing, carefully yaw the whole driveshaft to one side slowly, make sure you mark the splines location, must go exactly in same spot, lather the splines with same grease your grease gun has, reassemble, wipe excess grease off, drive...see what is....you may be surprised, I was....