As an after thought to previous reply,doing a google search for the shaft/worm gear same is a much sought after item,you can't blame husqvarna for part being discontinued as they probably don't make the actual auger drive,most mfg bid out parts/complete assembies for lowest price & have no control over quality of same,if part/assembly has poor workmanship,low grade parts,a high failure rate or part/assembly discontinued by mfg husqvarna may be stuck as well as customer for a replacement.
There could be a couple of reasons part failing/nla.
1-drive may have been made by peerless or a sub-contractor for peerless,for yrs tecumseh may have been playing both sides of the fence in that most snowblowers used tecumseh eng & peerless being a divison of tecumseh may have made auger drive & tecumseh would now sell eng/drive to snowblower mfg,over the yrs peerless or sub-contractor may have switched to a cast aluminum/stamped steel case to remain cost attractive to blower mfg,it may also be cause of drive failure.
2-husqvarna was buying cheap imported drives with a poor design/low quality parts in same & a cast aluminum/stamped steel case causeing a high failure rate & drive being discontinued by mfg.
Before rushing out & buying a new shaft/worm gear assembly I would carefully check case,bearing/bushing & shaft fit especially if case cast aluminum/stamped steel,the actual cause of problem may be worn case or worn bearings/bushings causeing mis-alignment of shaft & worm gear taking the beating.If there is case or bearing/bushing wear & you just replace shaft you're probably going to be looking for another shaft very soon.