My 450 snow thrower
 

I have a 450 on a 1641. Which realy throws well. I am at a cross roads though. I dont know if I want to keep dumping money in to it. The first snow of the winter, it just sat in the garage. I had to replace the electric clutch. The fourth or fith snow I blew a belt, and the last was the best yet. The splines of the shaft that the gearbox with the pulley slides in to, completly honed the end of the sfaft smooth. The actual gearbox and male end is fine. What it slides in to is what I guess is the blower shaft. To buy the entire group of parts is like three hundred bucks. All I'm looking for that shaft. So If some one has an suggestions, great! If not I'm willing to part with her. The 1641 runs great! Is rusty and I also have a steel and glass cab in very good shape w/wiper. Who knows I might just end up parting it out. I'd like to get rid of everything, or find a good deal on a blower and/or 1641, 1862 or 1863 one I can make one good machine out of.

The blower needs to be engaged at idle, as the rotating assembly has a LOT of inertia, and the more acceleration you impart on it, the more force is being applied to the splined shaft, causing what you have experienced. If you have been engaging it at idle, odds are whoever had it before you probably wasn't and damaged it. That wouldn't be doing the belt any favors, either. If you keep breaking belts, either you have worn out sheaves, bad idler, misalignment issues, or something like that. The cost of the parts is far cheaper than a newer (inferior) machine...

alg720 unless someone has changed the PTO pulley on the engine or changed the pulley on the gearbox that 1641 is suppose to have a 451 blower. As far as the gearbox goes not sure if the parts are NLA. Just went out to the garage and looked at a donor blower I have and the fan is what you will need. The shaft that goes to the spiral auger is pinned on the blade side of the fan and the gearbox slides into the other side.The blower fan in the garage is in about the same shape as what you describe. The splines aren't completely gone but are real close. If you are going to part it out I may be interested in it. I live in Cortland.

That's what I like about the old style mechanical clutches, you could engage them slowly, and ease the shock. It also saves wear on the clutch itself if you disengage them at idle.
I wish I could figure out a way to engage my electric pto more slowly. I put a new one on my diesel, and it slams in hard with my 50" deck.

At what point does a newer machine become a lesser machine? Cub doesnt make good tractors any more?

Is the "fan" you speak of, the second stage of the blower that throws the snow out the shoot?

Yes the blower fan is the 2nd stage that blows snow out of the chute.