how do I get the axle out?

 

These truck should have a c-clip rear axle, which mean the differential cover has to be removed. then you remove the bolt that holds the cross shaft in the differential so that the cross shaft can be removed. At that point the axle shaft can be pushed towards the center of the axle so the c-clip can be removed.

If I am wrong then removing the brake backing plates and bearing retainers will allow the axle to be removed by simply pulling it towards yourself. The brake backing plate will probably have to be removed either way.