clunking from rear axle

Me again....one thing after another. Hope this isnt too serious. Now that the shackle issue is over, I can focus on the next couple of things. When I first take off from a stop, there is a slight "clunking" noise coming from the rear end. It is not the U joints as one might suspect. They are new. Drive shafts are tight also. Its originating from the rear axle. Furthermore, even when coasting and I apply the gas, the clunk happens again, but not as noticable. Any ideas? Is there a rear end additive one dhould put in there much like the additive you would use for a posi unit? Axle is a D44 with 4.27 gearing. Have not had the cover off to inspect yet. I did jack up the rear end off the ground and rotated a wheel to the front then abrubtly to the rear and it appears as if there is some slippage? Almost duplicated the clunk, but not quite.
2nd thing...anyone have any good experiences they could share about swapping the speedo cluster/guages for a Krage unit? $89 at last glance. Was wanting to change it but wanted to check with the guru's first. All I really need is the fuel gauge and the temp...can that be done? Seems sealed to me.

Thanks for all the help...
Mike in KC

Semper Fi

 

loose axle nut
worn out axle key/keyway caused by above
broken wheel hub (crack in keyway)
worn out spider gears/pin-shaft loose in the case
worn axle splines/worn spider splines
loose lug nuts
loose pinion/yoke nut

 

I agree with jpflat2a and from my own personal experience,
I have had about the same thing happen once before and it was worn axle splines.
Then I had about the same thing happen once and it was spider gears.
Then, I had it happen another time and it was a tooth broken off the pinion gear.
I have exploded several other rear ends, but in those cases it was always obvious what was broken.

Pull the diff cover and see what everything looks like and check the gear oil for metal shavings, or like some of my experiences, big chunks of steel.

 

Could also be a posi unit with worn out clutches.