[legion]

I was considering the Idrive, but my garage door does not have transverse springs and I'd have to have those installed (was quoted $500 for that job alone--and I won't do springs myself).

The problem I was having with the old chain drive was that the chain would expand in the summer and contract in the winter--I had to retension it almost weekly. We were gone over Christmas, the temperature had dropped, and now the track was bowed upwards (about 2 inches high in the middle than the ends). The power unit had also developed an intermittent short--it often wouldn't work without percussive maintenance.

Also, the bracing on the old power unit was hodge-podge at best, it would shake and sway considerably when opened or closed. Because the new unit is much lighter and closer to the ceiling, I used less bracing but used it more effectively.