Drive line noise mystery? Solved

[alborz]

I'm trying to see if other peterbilt 387s leaf springs are flat or arc shape "between the hanger to the chasee and where it sits on the top of the axles " on all four springs.
I noticed two of my springs are flat and two are arc shaped.
So Please those who have Peterbilt 387 inspect their rear axles and note their air leaf springs and Kindly report back here their findings.

thank you in advance for your help