A revolver shackle is a shackle that is hinged in the middle. It basically rides folded up on itself but when the axle droops, it unfolds to allow for more travel, while a fixed shackle only has forward and backword movement according to the compression of the springs. I talked to a Terra Mnfg Rep at an offroad show last week who said the revolvers weren't actually designed for the weight of a fullsize, but there are people here who run them OK I think.
Tom