Saw Mill It looks like you'll need seal work on those rear ones,you will have to take the axles out,if the drum will come off over the hub you could then inspect it. On a chevy I noticed a bearing too warm and was able to loosen it without disturbing the (not leaking seal) and saved it. I've learned not to overfill the differential and overtax the seals. Aim to end up with oil level 1/2 inch below the fill plug hole cold on the level. Front ones as was said,take off as an assembly after loosening the shoes. Once your back together drive a little feel your hubs should be barely warm from brake drum heat,I drive 12 miles feel em bout like a cucumber, you know not hot. Good Luck great truck too GMC tough !!
