Hi, I am attempting to replace on of my garage door openers. We have two, in one of them the gears somehow were ground to powder (Which is why we're replacing it). The current model is a Sears Craftsman 1/2 hp chain drive from 1984. Money is an issue, so I was considering buying a cheaper model Chamberlain chain drive. I was wondering if there are any disadvantages/advantages with screw and belt drives vs. chain drives? We've never had a problem with our current chain drive except that noise has increased over the past few years. Are there issues with either of these I need to know about? I'm thinking a belt drive could end up with a stretched belt but I've never worked with one so I'm not sure... Any input appreciated.