Strange noise

[RedRoad]

Been trying to isolate a strange noise I get on decel/coast from 65 down to 10 mph. It is speed dependent and slows down as speed is decreased.

Sounds like a bent rim causing the lugs on the mud terrain to make noise on rotation or a wasted ball joint on the front end, kind of a wha, wha, wha noise.

Ive replaced the rims, tires, ball joints, tie rods, all u joints and all wheel bearings. Ive verified that the rims are not bent or any of the tires are out of round.

Today when getting off the freeway I put the truck in neutral to see if hear the noise more clearly reflecting off the off ramp wall and realized the noise was gone! Tried it a few more times and if the trans (TH350) or t case (NP205) is in neutral there is no noise.

The trans is rebuilt and the adapter has new bearings and seals which brings me down to the t case, coupler, rear end or drive shaft.

Drive shaft looks to be the original with a slight amount of play in the splines, it still has the original HO52 and NP205. I was going to replace the rear with a 14 bolt out of a 74 1 ton as there is a bit of moaning at speed coming from somewhere.

Is there any way to isolate the noise before I keep throwing cash at it?