Apologies Alex, a 'bum steer', the felt washers are on the LT230 box not the diffs.

 

OR, the noises on your second vid sound familiarly like autobox issues, I had exactly the same noise as the final rapid clicking noise when placed into P Park whilst filling the box with ATF and the transfer box in neutral. I think it's the sprags catching but it shouldn't be a problem but don't risk it too often. I reckon it happens when the transfer box isn't fully engaged in hi or lo and is still in neutral and the torque converter and gearbox is spinning with the engine running but unrestrained by the transfer box. Firstly move the truck in hi transfer and drive it a short distance and also check your ATF autobox oil level.