Garage door only opens a foot above ground

by Terry
(Flowery Branch, Ga)

I have a Challenger 9300 opener. It raises about 12 inches then slams back down. If I assist it past that point on the lift, it will continue up and fully open. it has no problem closing from full open.

I noticed the top of the garage door seems to have been rubbing along the bottom of the track the chain rides in. I put lithium grease on it, but that didnt do anything but cause it to slam close faster. The track doesnt appear to have moved or slipped from the position it was in.

What's my problem?