Originally Posted by Irelands child
If it has a Sears door opener and those gears are trashed, you can buy a set of gears for less then 10 bucks or an entire rebuild kit for about $25 - and ebay is the least expensive, whichever way you go. It will take you about 2 hours the first time, 30 minutes the next.
As far as a new spring, get both sides. Both HD and Lowe's carry them. Take one of the old ones with you to match.
Safety cables saved me from a clonk on my thinly haired scalp - again, HD or Lowes have kits or cheaper yet, some cable and clamps.
I used the full gear kit, but also have rebuilt this shaft and gear set for the next time or for the other door:
That looks very familiar, rebuilt ours about 6 months ago. I bought the gear on ebay. think it was $6.
I am not a believer in the big hp thing with openers. I don't see where it makes much difference at all unless it operates at a faster feet per minute.
1/2 hp or 1 hp they use the same nylon gears, so if the motor rpm is the same, then the only speed change would be with a sprocket. (chain drive)
I do not believe there is a discernible difference in the weight of a garage door when the counter balance springs are PROPERLY adjusted. The door should only need 10# or so of force to lift it.
I prefer the torsion springs over the extension springs as they are far more adjustible.
Just $.02 worth of my rambling thoughts.