2000 F250 clunking from rear while coasting

[lasmacgod]

I have a 2000 F250 4x4 V10 Auto, crew cab short bed. 196k miles. Stock wheels/tires.

I changed out the gears from 3.73 to 4.30's. On my test drive, I noticed a rhythmic clunking noise coming from the rear half of the truck while coasting from 30 or 35 mph to about 5 mph. It is not loud, I can't really hear it with the radio or A/C on. Pulled everything back apart, all checked out. Yes, using 75W-140 synthetic with LS additive. The carrier was showing excessive spider gear wear due to a failure of the LS clutches, so I figured it might be that.

The center support bearing and u-joints were original, and I replaced them. I figured I got good life out of them, especially being OE.

I tore into the rear end a couple weeks later, and replaced the carrier with the updated 3-pinion design with LS. Everything looks good, still specs out. Problem still there. The clunking follows the speed of the tires, not the drive shaft. Not sure if it makes the noise while turning, as I don't have many opportunities to turn at speed high enough to give the noise. If I accelerate from a coast, the noise stops. The noise also seems to stop when I apply the brakes briskly. Applying the brakes with light pressure just muffles the clunking noise.

Anybody have any ideas?

[lasmacgod]

Ok, threw the rear axle up on stands, and had the wife run the go-pedal while I crawled around underneath the truck. The clunking or hammering noise is definitely coming from the rear differential, but I just cannot find the problem for the life of me. It is only on coast-down, and I can hear it and feel it when I put my hand on the center section. It is consistent with full rotation of the tires, leading me to believe it is somewhere in the differential/ring gear.

Having had this apart 3 times after installing the gears, I cannot figure this out. The only thing I can think of is possibly a high spot on one of the ring gear teeth. Anybody with any ideas?