I have a Murray/Noma snowblower. I have to replace one of the augers. It is a two stage blower. I can't figure out how to remove the old auger. I removed the screws supporting the auger on each side of the housing but the center gearbox is tied to the impeller and wonder if someone can give me an idea of how to remove the assembly. I thought either the auger assembly would have slid off the impeller shaft or the auger/impeller assembly would have slid out of the motor housing. The exploded parts view does not show any retaining rings anywhere. Do I have to disassemble the auger gearbox?