How to Shorten a Chain Drive Opener

Our customer received a Craftsman garage door opener for Christmas and called us out to install it. It looked like a typical install.  So I took the new unit out of the box along with all the parts. I assembled everything on the garage floor and then took down their old Genie.

I lifted the new opener up to install it. This garage has a header or structure support protruding down from the ceiling just behind the door when it’s up.

Garage Door HeaderThe new opener is about 10′ long. The header is 9’6″ from the header above the door. In short this means the opener I just assembled is about 6″ too long to install. It would not fit. I could either take it apart and put it back in the box so they could return it or I could modify the opener to fit.

I already had their old opener down and the new one assembled so I decided to modify the opener. I needed to cut down the opener rail and the drive chain by about 6 1/2″. I cut the rail down 6 1/2″ and then I had to cut the chain down 13″.  I had to cut the chain down double the length that the rail was cut.  The chain is a loop so it had to be cut down the length of the rail that was cut.

Tools used to modify a garage door opener.

If you have to cut any more than 6″ off of the opener it won’t open a 7′ garage door all the way. I had a couple inches to spare.  I then reassembled the opener and installed it.

This install would have been easier if the new opener were a screw drive instead of a chain drive.  In a screw drive there is not a chain to cut or master links to bother with. You simply cut the screw rail down to the desired length and install.

Hope this information and pictures help when dealing with a garage door opener that will not fit.

Garage Door Opener cut down

Modified chain drive garage door opener installed.