i took out my np249 transfercase to put in a new VC, got it all apart and didnt see any signs of wear on any parts, and since i had the thing out i put all new RTV gaskets in it because they where leaking, and a new oil seal for the rear slip yolk. so i put it all together and put it back in, i filled it with dexron III, my haynes manual said so AND the computer at advance autoparts said so. know it still pops like crazy and my speedometer doesnt work (it threw a CEL)

 

if you have a mechanical speedo, it should run off the transmission not the transfercase. as for the poping noises, have you checked the hub bearings and cv joints in the axle shafts?

 

i took out a plastic gear from my transfercase that was hooked to some wire harness, i was told it was a speedo... and i didnt think it was the cv joints because it feels like its coming from the rear, and im not sure what HUB bearings are, is it the same thing as the axle pinion bearing?